What’s Vulnerable › Vulnerabilities

CVE-2015-1853

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-12-09 · updated 2026-06-17

Description

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.

Affected products

• chrony: before 1.31.1 — fixed in 1.31.1

How to fix

Upgrade to a fixed version: chrony 1.31.1. Check the vendor advisory for mitigations.

References

• http://chrony.tuxfamily.org/News.html
• https://security.gentoo.org/glsa/201507-01
• http://chrony.tuxfamily.org/News.html
• https://security.gentoo.org/glsa/201507-01

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