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CVE-2015-1853· NVD / CVE Program· CNA redhat

chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers wi

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.

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Dec 9, 2019
Updated
Jun 16, 2026
EPSS
1.7% · 76th percentile
CWE
—
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Report tools

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Action score

27

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 1.7%

Noroxi analysis

No Noroxi analysis for this record yet

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Affected systems

VendorProduct
tuxfamilychrony

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • tuxfamily chronybefore 1.31.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • chrony chrony

    • before 1.31.1affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12chronybefore 1.30-21.30-2
Debian:6.0chronybefore 1.24-3+squeeze21.24-3+squeeze2
Debian:7chronybefore 1.24-3.1+deb7u31.24-3.1+deb7u3
Red Hat:enterprise_linux:7::clientchronybefore 0:2.1.1-1.el70:2.1.1-1.el7
Red Hat:enterprise_linux:7::clientchrony-debuginfobefore 0:2.1.1-1.el70:2.1.1-1.el7

Same product

tuxfamily: all records

Other highest-scoring records for the same primary product.

  • CVE-2016-1567chrony before 1.31.2 and 2.x before 2.2.1 do not verify peer associations of symmetric keys when authenticating packets, which might allow r
    33Monitor
  • CVE-2015-1821Heap-based buffer overflow in chrony before 1.31.1 allows remote authenticated users to cause a denial of service (chronyd crash) or possibl
    27Monitor
  • CVE-2020-14367A flaw was found in chrony versions before 3.5.1 when creating the PID file under the /var/run/chrony folder.
    24Monitor
  • CVE-2012-4503cmdmon.c in Chrony before 1.29 allows remote attackers to obtain potentially sensitive information from stack memory via vectors related to
    21Monitor
  • CVE-2012-4502Multiple integer overflows in pktlength.c in Chrony before 1.29 allow remote attackers to cause a denial of service (crash) via a crafted (1
    21Monitor
  • CVE-2010-0294chronyd in Chrony before 1.23.1, and possibly 1.24-pre1, generates a syslog message for each unauthorized cmdmon packet, which allows remote
    21Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:chrony1.30-2 · Debian:12Package registry (OSV)
red hat:chrony0:2.1.1-1.el7 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:chrony-debuginfo0:2.1.1-1.el7 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records