CVE-2015-1853
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.
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
What each source reports
NVD Score used
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 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 4.0 Medium
AV: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
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 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSV
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 Medium
CVSS: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
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 Medium
CVSS: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
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 Medium
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
chronyDebian:12 |
before 1.30-2 | 1.30-2 |
chronyDebian:13 |
before 1.30-2 | 1.30-2 |
chronyDebian:14 |
before 1.30-2 | 1.30-2 |
chronyDebian:6.0 From an advisory covering 3 CVEs |
before 1.24-3+squeeze2, plus listed versions 1.24-31.24-3+squeeze1 |
1.24-3+squeeze2 |
chronyDebian:7 From an advisory covering 3 CVEs |
before 1.24-3.1+deb7u3, plus listed versions 1.24-3.1+deb7u11.24-3.1+deb7u2 |
1.24-3.1+deb7u3 |
chronyMageia:4 From an advisory covering 3 CVEs |
before 1.29.1-1.1.mga4 | 1.29.1-1.1.mga4 |
chronyRed Hat:enterprise_linux:7::client From an advisory covering 3 CVEs |
before 0:2.1.1-1.el7 | 0:2.1.1-1.el7 |
chrony-debuginfoRed Hat:enterprise_linux:7::client From an advisory covering 3 CVEs |
before 0:2.1.1-1.el7 | 0:2.1.1-1.el7 |
chronyRed Hat:enterprise_linux:7::computenode From an advisory covering 3 CVEs |
before 0:2.1.1-1.el7 | 0:2.1.1-1.el7 |
chrony-debuginfoRed Hat:enterprise_linux:7::computenode From an advisory covering 3 CVEs |
before 0:2.1.1-1.el7 | 0:2.1.1-1.el7 |
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| Package | Affected | Fixed |
|---|---|---|
chronyRed Hat:enterprise_linux:7::server From an advisory covering 3 CVEs |
before 0:2.1.1-1.el7 | 0:2.1.1-1.el7 |
chrony-debuginfoRed Hat:enterprise_linux:7::server From an advisory covering 3 CVEs |
before 0:2.1.1-1.el7 | 0:2.1.1-1.el7 |
chronyRed Hat:enterprise_linux:7::workstation From an advisory covering 3 CVEs |
before 0:2.1.1-1.el7 | 0:2.1.1-1.el7 |
chrony-debuginfoRed Hat:enterprise_linux:7::workstation From an advisory covering 3 CVEs |
before 0:2.1.1-1.el7 | 0:2.1.1-1.el7 |
chronyUbuntu:14.04:LTS |
before 1.29-1ubuntu0.1, plus listed versions 1.26-41.29-1 |
1.29-1ubuntu0.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
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.
References
security.gentoo.org/glsa/201507-01
chrony.tuxfamily.org/News.html
nvd.nist.gov/vuln/detail/CVE-2015-1853
access.redhat.com/errata/RHSA-2015:2241
bugzilla.redhat.com/show_bug.cgi?id=1209572
Show 24 moreShow less
github.com/advisories/GHSA-gf8j-j7q8-vhh5
security-tracker.debian.org/tracker/CVE-2015-1853
advisories.mageia.org/MGASA-2015-0163.html
bugs.mageia.org/show_bug.cgi?id=15647
debian.org/security/2015/dsa-3222
security.access.redhat.com/data/csaf/v2/advisories/2015/rhsa-2015_2241.json
cve.org/CVERecord?id=CVE-2015-1821
ubuntu.com/security/CVE-2015-1853
openwall.com/lists/oss-security/2015/04/07/10