According to its self-reported version, the IOS XE is affected by one or more vulnerabilities. Please see the included Cisco BIDs and the Cisco Security Advisory for more information.

According to the versions of the ntp packages installed, the EulerOS Virtualization installation on the remote host is affected by the following vulnerabilities :

  - It was found that when ntp is configured with rate     limiting for all associations the limits are also     applied to responses received from its configured     sources. A remote attacker who knows the sources can     cause a denial of service by preventing ntpd from     accepting valid responses from its     sources.(CVE-2016-7426)

  - ntpq in NTP before 4.2.8p7 allows remote attackers to     obtain origin timestamps and then impersonate peers via     unspecified vectors.(CVE-2015-8139)

  - A NULL pointer dereference flaw was found in the way     ntpd processed 'ntpdc reslist' commands that queried     restriction lists with a large amount of entries. A     remote attacker could potentially use this flaw to     crash ntpd.(CVE-2015-7977)

  - A vulnerability was found in NTP, in the parsing of     packets from the /dev/datum device. A malicious device     could send crafted messages, causing ntpd to     crash.(CVE-2017-6462)

  - The process_packet function in ntp_proto.c in ntpd in     NTP 4.x before 4.2.8p8 allows remote attackers to cause     a denial of service (peer-variable modification) by     sending spoofed packets from many source IP addresses     in a certain scenario, as demonstrated by triggering an     incorrect leap indication.(CVE-2016-4954)

  - It was found that ntpd could crash due to an     uninitialized variable when processing malformed     logconfig configuration commands.(CVE-2015-5194)

  - It was discovered that the sntp utility could become     unresponsive due to being caught in an infinite loop     when processing a crafted NTP packet.(CVE-2015-5219)

  - It was discovered that ntpd as a client did not     correctly check the originate timestamp in received     packets. A remote attacker could use this flaw to send     a crafted packet to an ntpd client that would     effectively disable synchronization with the server, or     push arbitrary offset/delay measurements to modify the     time on the client.(CVE-2015-8138)

  - It was found that the fix for CVE-2014-9750 was     incomplete: three issues were found in the value length     checks in NTP's ntp_crypto.c, where a packet with     particular autokey operations that contained malicious     data was not always being completely validated. A     remote attacker could use a specially crafted NTP     packet to crash ntpd.(CVE-2015-7702)

  - Multiple buffer overflow flaws were discovered in     ntpd's crypto_recv(), ctl_putdata(), and configure()     functions. A remote attacker could use either of these     flaws to send a specially crafted request packet that     could crash ntpd or, potentially, execute arbitrary     code with the privileges of the ntp user. Note: the     crypto_recv() flaw requires non default configurations     to be active, while the ctl_putdata() flaw, by default,     can only be exploited via local attackers, and the     configure() flaw requires additional authentication to     exploit.(CVE-2014-9295)

  - It was found that an ntpd client could be forced to     change from basic client/server mode to the interleaved     symmetric mode. A remote attacker could use a spoofed     packet that, when processed by an ntpd client, would     cause that client to reject all future legitimate     server responses, effectively disabling time     synchronization on that client.(CVE-2016-1548)

  - A flaw was found in the way NTP's libntp performed     message authentication. An attacker able to observe the     timing of the comparison function used in packet     authentication could potentially use this flaw to     recover the message digest.(CVE-2016-1550)

  - A denial of service flaw was found in the way NTP     handled preemptable client associations. A remote     attacker could send several crypto NAK packets to a     victim client, each with a spoofed source address of an     existing associated peer, preventing that client from     synchronizing its time.(CVE-2016-1547)

  - It was found that the fix for CVE-2014-9750 was     incomplete: three issues were found in the value length     checks in NTP's ntp_crypto.c, where a packet with     particular autokey operations that contained malicious     data was not always being completely validated. A     remote attacker could use a specially crafted NTP     packet to crash ntpd.(CVE-2015-7692)

  - A flaw was found in the way the ntpq client processed     certain incoming packets in a loop in the getresponse()     function. A remote attacker could potentially use this     flaw to crash an ntpq client instance.(CVE-2015-8158)

  - It was discovered that ntpd as a client did not     correctly check timestamps in Kiss-of-Death packets. A     remote attacker could use this flaw to send a crafted     Kiss-of-Death packet to an ntpd client that would     increase the client's polling interval value, and     effectively disable synchronization with the     server.(CVE-2015-7704)

  - A flaw was found in the control mode functionality of     ntpd. A remote attacker could send a crafted control     mode packet which could lead to information disclosure     or result in DDoS amplification attacks.(CVE-2016-9310)

  - A vulnerability was discovered in the NTP server's     parsing of configuration directives. A remote,     authenticated attacker could cause ntpd to crash by     sending a crafted message.(CVE-2017-6464)

  - It was found that ntpd automatically generated weak     keys for its internal use if no ntpdc request     authentication key was specified in the ntp.conf     configuration file. A remote attacker able to match the     configured IP restrictions could guess the generated     key, and possibly use it to send ntpdc query or     configuration requests.(CVE-2014-9293)

  - A denial of service flaw was found in the way NTP hosts     that were peering with each other authenticated     themselves before updating their internal state     variables. An attacker could send packets to one peer     host, which could cascade to other peers, and stop the     synchronization process among the reached     peers.(CVE-2015-1799)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Brief introduction 

CVE-2015-1798

When ntpd is configured to use a symmetric key to authenticate a remote NTP server/peer, it checks if the NTP message authentication code (MAC) in received packets is valid, but not if there actually is any MAC included. Packets without a MAC are accepted as if they had a valid MAC. This allows a MITM attacker to send false packets that are accepted by the client/peer without having to know the symmetric key.
The attacker needs to know the transmit timestamp of the client to match it in the forged reply and the false reply needs to reach the client before the genuine reply from the server. The attacker doesn't necessarily need to be relaying the packets between the client and the server. Authentication using autokey doesn't have this problem as there is a check that requires the key ID to be larger than NTP_MAXKEY, which fails for packets without a MAC.

CVE-2015-1799

An attacker knowing that NTP hosts A and B are peering with each other (symmetric association) can send a packet to host A with source address of B which will set the NTP state variables on A to the values sent by the attacker. Host A will then send on its next poll to B a packet with originate timestamp that doesn't match the transmit timestamp of B and the packet will be dropped. If the attacker does this periodically for both hosts, they won't be able to synchronize to each other. This is a known denial of service attack, described at https://www.eecis.udel.edu/~mills/onwire.html . According to the document the NTP authentication is supposed to protect symmetric associations against this attack, but that doesn't seem to be the case. The state variables are updated even when authentication fails and the peers are sending packets with originate timestamps that don't match the transmit timestamps on the receiving side.

ntp-keygen on big endian hosts

Using ntp-keygen to generate an MD5 key on big endian hosts resulted in either an infite loop or an key of only 93 possible keys.

NOTE: Tenable Network Security has extracted the preceding description block directly from the DLA security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Security fix for CVE-2015-1799, CVE-2015-1798, #1210324

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The symmetric-key feature in the receive function in ntp_proto.c in ntpd in NTP 4.x before 4.2.8p2 requires a correct MAC only if the MAC field has a nonzero length, which makes it easier for man-in-the-middle attackers to spoof packets by omitting the MAC.
(CVE-2015-1798)

The symmetric-key feature in the receive function in ntp_proto.c in ntpd in NTP 3.x and 4.x before 4.2.8p2 performs state-variable updates upon receiving certain invalid packets, which makes it easier for man-in-the-middle attackers to cause a denial of service (synchronization loss) by spoofing the source IP address of a peer.
(CVE-2015-1799)

This update also addresses leap-second handling. With older ntp versions, the -x option was sometimes used as a workaround to avoid kernel inserting/deleting leap seconds by stepping the clock and possibly upsetting running applications. That no longer works with 4.2.6 as ntpd steps the clock itself when a leap second occurs. The fix is to treat the one second offset gained during leap second as a normal offset and check the stepping threshold (set by -x or tinker step) to decide if a step should be applied. See this forum post for more information on the Amazon Linux AMI's leap-second handling.

ntp was updated to fix two security related flaws as well as 'slew' mode handling for leap seconds.

The following vulnerabilities were fixe :

  - ntpd could accept unauthenticated packets with symmetric     key crypto. (CVE-2015-1798)

  - ntpd authentication did not protect symmetric     associations against DoS attacks (CVE-2015-1799)

  - ntp-keygen may generate non-random symmetric keys on     big-endian systems (bsc#928321, CVE-2015-3405).

The update package also includes non-security fixes. See advisory for details.

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-9297 Network Time Protocol (NTP) Project NTP daemon (ntpd) could allow a remote attacker to conduct spoofing attacks, caused by insufficient entropy in PRNG. An attacker could exploit this vulnerability to spoof the IPv6 address ::1 to bypass ACLs and launch further attacks on the system. Network Time Protocol (NTP) Project NTP daemon (ntpd) is vulnerable to a denial of service, caused by an error when using symmetric key authentication. By sending specially-crafted packets to both peering hosts, an attacker could exploit this vulnerability to prevent synchronization.

The remote Redhat Enterprise Linux 6 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2015:1459 advisory.

    The Network Time Protocol (NTP) is used to synchronize a computer's time     with another referenced time source.

    It was found that because NTP's access control was based on a source IP     address, an attacker could bypass source IP restrictions and send malicious     control and configuration packets by spoofing ::1 addresses.
    (CVE-2014-9298)

    A denial of service flaw was found in the way NTP hosts that were peering     with each other authenticated themselves before updating their internal     state variables. An attacker could send packets to one peer host, which     could cascade to other peers, and stop the synchronization process among     the reached peers. (CVE-2015-1799)

    A flaw was found in the way the ntp-keygen utility generated MD5 symmetric     keys on big-endian systems. An attacker could possibly use this flaw to     guess generated MD5 keys, which could then be used to spoof an NTP client     or server. (CVE-2015-3405)

    A stack-based buffer overflow was found in the way the NTP autokey protocol     was implemented. When an NTP client decrypted a secret received from an NTP     server, it could cause that client to crash. (CVE-2014-9297)

    It was found that ntpd did not check whether a Message Authentication Code     (MAC) was present in a received packet when ntpd was configured to use     symmetric cryptographic keys. A man-in-the-middle attacker could use this     flaw to send crafted packets that would be accepted by a client or a peer     without the attacker knowing the symmetric key. (CVE-2015-1798)

    The CVE-2015-1798 and CVE-2015-1799 issues were discovered by Miroslav     Lichvr of Red Hat.

    Bug fixes:

    * The ntpd daemon truncated symmetric keys specified in the key file to 20     bytes. As a consequence, it was impossible to configure NTP authentication     to work with peers that use longer keys. The maximum length of keys has now     been changed to 32 bytes. (BZ#1053551)

    * The ntp-keygen utility used the exponent of 3 when generating RSA keys,     and generating RSA keys failed when FIPS mode was enabled. ntp-keygen has     been modified to use the exponent of 65537, and generating keys in FIPS     mode now works as expected. (BZ#1184421)

    * The ntpd daemon included a root delay when calculating its root     dispersion. Consequently, the NTP server reported larger root dispersion     than it should have and clients could reject the source when its distance     reached the maximum synchronization distance (1.5 seconds by default).
    Calculation of root dispersion has been fixed, the root dispersion is now     reported correctly, and clients no longer reject the server due to a large     synchronization distance. (BZ#1045376)

    * The ntpd daemon dropped incoming NTP packets if their source port was     lower than 123 (the NTP port). Clients behind Network Address Translation     (NAT) were unable to synchronize with the server if their source port was     translated to ports below 123. With this update, ntpd no longer checks the     source port number. (BZ#1171630)

    Enhancements:

    * This update introduces configurable access of memory segments used for     Shared Memory Driver (SHM) reference clocks. Previously, only the first two     memory segments were created with owner-only access, allowing just two SHM     reference clocks to be used securely on a system. Now, the owner-only     access to SHM is configurable with the mode option, and it is therefore     possible to use more SHM reference clocks securely. (BZ#1122015)

    * Support for nanosecond resolution has been added to the SHM reference     clock. Prior to this update, when a Precision Time Protocol (PTP) hardware     clock was used as a time source to synchronize the system clock (for     example, with the timemaster service from the linuxptp package), the     accuracy of the synchronization was limited due to the microsecond     resolution of the SHM protocol. The nanosecond extension in the SHM     protocol now enables sub-microsecond synchronization of the system clock.
    (BZ#1117704)

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Cisco Application Control Engine (ACE) software installed on the remote Cisco ACE 4710 device or ACE30 module is version A5 prior to A5(3.3). It is, therefore, affected by multiple vulnerabilities :

  - An invalid free memory error exists due to improper     validation of user-supplied input when a DTLS peer     receives application data between ChangeCipherSpec and     Finished messages. A remote attacker can exploit this to     corrupt memory, resulting in a denial of service or     the execution of arbitrary code. (CVE-2014-8176)

  - A denial of service vulnerability exists when processing     an ECParameters structure due to an infinite loop that     occurs when a specified curve is over a malformed binary     polynomial field. A remote attacker can exploit this to     perform a denial of service against any system that     processes public keys, certificate requests, or     certificates. This includes TLS clients and TLS servers     with client authentication enabled. (CVE-2015-1788)

  - A denial of service vulnerability exists due to improper     validation of the content and length of the ASN1_TIME     string by the X509_cmp_time() function. A remote     attacker can exploit this, via a malformed certificate     and CRLs of various sizes, to cause a segmentation     fault, resulting in a denial of service condition. TLS     clients that verify CRLs are affected. TLS clients and     servers with client authentication enabled may be     affected if they use custom verification callbacks.
    (CVE-2015-1789)

  - A NULL pointer dereference flaw exists in the PKCS#7     parsing code due to incorrect handling of missing inner     'EncryptedContent'. This allows a remote attacker, via     specially crafted ASN.1-encoded PKCS#7 blobs with     missing content, to cause a denial of service condition     or other potential unspecified impacts. (CVE-2015-1790)

  - A double-free error exists due to a race condition that     occurs when a NewSessionTicket is received by a     multi-threaded client when attempting to reuse a     previous ticket. A remote attacker can exploit this to     cause a denial of service condition or other potential     unspecified impact. (CVE-2015-1791)

  - A denial of service vulnerability exists in the CMS code     due to an infinite loop that occurs when verifying a     signedData message. A remote attacker can exploit this     to cause a denial of service condition. (CVE-2015-1792)

  - The symmetric-key feature in the receive function     requires a correct message authentication code (MAC)     only if the MAC field has a nonzero length. This makes     it easier for a man-in-the-middle attacker to spoof     packets by omitting the MAC. (CVE-2015-1798)

  - A flaw exists in the symmetric-key feature in the     receive function when handling a specially crafted     packet sent to one of two hosts that are peering with     each other. This allows an attacker to cause the next     attempt by the servers to synchronize to fail.
    (CVE-2015-1799)

  - A man-in-the-middle vulnerability, known as Logjam,     exists due to a flaw in the SSL/TLS protocol. A remote     attacker can exploit this flaw to downgrade connections     using ephemeral Diffie-Hellman key exchange to 512-bit     export-grade cryptography. (CVE-2015-4000)

  - A flaw exists in the TLS 1.x implementation in the     Cavium SDK due to a failure to check the first byte of     the padding bytes. A man-in-the-middle attacker can     exploit this, by sending specially crafted requests to     the server, to induce requests that allow determining     the plaintext chunks of data. This vulnerability is a     variant of the POODLE attack. (CVE-2015-4595)

ID	名稱	產品	系列	已發布	已更新	嚴重性
108955	Cisco IOS XE Software Multiple Vulnerabilities in ntpd (cisco-sa-20150408-ntpd)	Nessus	CISCO	2018/4/10	2021/6/28	medium
125008	EulerOS Virtualization 3.0.1.0 : ntp (EulerOS-SA-2019-1555)	Nessus	Huawei Local Security Checks	2019/5/14	2024/5/22	high
82715	Debian DLA-192-1 : ntp security update	Nessus	Debian Local Security Checks	2015/4/13	2021/1/11	medium
83010	Fedora 20 : ntp-4.2.6p5-22.fc20 (2015-5874)	Nessus	Fedora Local Security Checks	2015/4/23	2021/1/11	medium
83271	Amazon Linux AMI : ntp (ALAS-2015-520)	Nessus	Amazon Linux Local Security Checks	2015/5/7	2018/4/18	medium
83725	SUSE SLED12 / SLES12 Security Update : ntp (SUSE-SU-2015:0865-1)	Nessus	SuSE Local Security Checks	2015/5/20	2021/1/6	high
84493	AIX 7.1 TL 0 : ntp4 (IV71096)	Nessus	AIX Local Security Checks	2015/7/2	2023/4/21	medium
84951	RHEL 6 : ntp (RHSA-2015:1459)	Nessus	Red Hat Local Security Checks	2015/7/23	2025/8/29	high
91427	Cisco ACE 4710 Appliance / ACE30 Module Multiple Vulnerabilities (Logjam)	Nessus	CISCO	2016/6/1	2022/12/5	high

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