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CVE-2015-1853

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP...

6.5 MediumFix available

CVE-2015-1853 is a medium vulnerability (CVSS 6.5) in Chrony, published April 12, 2015. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.70%, the 77th percentile. Fixed in chrony 1.30-2.

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

1.70%Up 0.6 points since Feb 4, 2022
90%50%10%1%

What each source reports

NVD Score used 6.5

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

Record
CVE-2015-1853
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
4.0 MediumAV:N/AC:L/Au:S/C:N/I:N/A:P
Updated
2026-11-02
CVE List No score

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

Record
CVE-2015-1853
Updated
2026-11-02
EUVDEUVD-2015-1962 No score

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

Record
EUVD-2015-1962
Updated
2026-11-03
GitHub AdvisoriesGHSA-gf8j-j7q8-vhh5 6.5

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP...

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

Record
GHSA-gf8j-j7q8-vhh5
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSV 6.5

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

Record
CVE-2015-1853
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2015-1853 6.5

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

Record
DEBIAN-CVE-2015-1853
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2015-1853 6.5

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers with knowledge of NTP peering to cause a denial of service (inability to synchronize) via random timestamps in crafted NTP data packets.

Record
UBUNTU-CVE-2015-1853
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVMGASA-2015-0163 No score

Updated chrony packages fix security vulnerabilities

Updated chrony package fixes security vulnerabilities:

Using particular address/subnet pairs when configuring access control would cause an invalid memory write. This could allow attackers to cause a denial of service (crash) or execute arbitrary code (CVE-2015-1821).

When allocating memory to save unacknowledged replies to authenticated command requests, a pointer would be left uninitialized, which could trigger an invalid memory write. This could allow attackers to cause a denial of service (crash) or execute arbitrary code (CVE-2015-1822).

When peering with other NTP hosts using authenticated symmetric association, the internal state variables would be updated before the MAC of the NTP messages was validated. This could allow a remote attacker to cause a denial of service by impeding synchronization between NTP peers (CVE-2015-1853).

Record
MGASA-2015-0163
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
chrony
Debian:12
 before 1.30-2
1.30-2
chrony
Debian:13
 before 1.30-2
1.30-2
chrony
Debian:14
 before 1.30-2
1.30-2
chrony
Debian:6.0
 before 1.24-3+squeeze2, plus listed versions
1.24-31.24-3+squeeze1
1.24-3+squeeze2
chrony
Debian:7
 before 1.24-3.1+deb7u3, plus listed versions
1.24-3.1+deb7u11.24-3.1+deb7u2
1.24-3.1+deb7u3
chrony
Mageia:4
 before 1.29.1-1.1.mga4
1.29.1-1.1.mga4
chrony
Red Hat:enterprise_linux:7::client
 before 0:2.1.1-1.el7
0:2.1.1-1.el7
chrony-debuginfo
Red Hat:enterprise_linux:7::client
 before 0:2.1.1-1.el7
0:2.1.1-1.el7
chrony
Red Hat:enterprise_linux:7::computenode
 before 0:2.1.1-1.el7
0:2.1.1-1.el7
chrony-debuginfo
Red Hat:enterprise_linux:7::computenode
 before 0:2.1.1-1.el7
0:2.1.1-1.el7
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Affected packages
PackageAffectedFixed
chrony
Red Hat:enterprise_linux:7::server
 before 0:2.1.1-1.el7
0:2.1.1-1.el7
chrony-debuginfo
Red Hat:enterprise_linux:7::server
 before 0:2.1.1-1.el7
0:2.1.1-1.el7
chrony
Red Hat:enterprise_linux:7::workstation
 before 0:2.1.1-1.el7
0:2.1.1-1.el7
chrony-debuginfo
Red Hat:enterprise_linux:7::workstation
 before 0:2.1.1-1.el7
0:2.1.1-1.el7
chrony
Ubuntu:14.04:LTS
 before 1.29-1ubuntu0.1, plus listed versions
1.26-41.29-1
1.29-1ubuntu0.1

History

History
WhenChangedSources
2026-11-03aliasesEUVD
2026-11-02createdCVE List, GitHub Advisories, NVD, OSV

References

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