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CVE-2015-1821· NVD / CVE Program· CNA redhat

Heap-based buffer overflow in chrony before 1.31.1 allows remote authenticated users to cause a denial of service (chronyd crash) or possibl

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 3.4% (FIRST EPSS); higher than 88.5% of all records.
  • No special conditions are required; it is repeatable.
  • Fixed version: chrony (Debian:12) 1.30-2; chrony (Debian:6.0) 1.24-3+squeeze2; chrony (Debian:7) 1.24-3.1+deb7u3.

Low priority for now. Upgrade to chrony (Debian:12) 1.30-2; chrony (Debian:6.0) 1.24-3+squeeze2; chrony (Debian:7) 1.24-3.1+deb7u3 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Heap-based buffer overflow in chrony before 1.31.1 allows remote authenticated users to cause a denial of service (chronyd crash) or possibly execute arbitrary code by configuring the (1) NTP or (2) cmdmon access with a subnet size that is indivisible by four and an address with a nonzero bit in the subnet remainder.

MediumCVSS 6.5 · v2.0—No exploit Fix available
Published
Apr 16, 2015
Updated
Jun 16, 2026
EPSS
3.4% · 89th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 3.4%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
tuxfamilychrony
debiandebian linux

Affected versions

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

  • debian debian linux7.0
  • tuxfamily chronyup to 1.31 inclusive

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-2015-1853chrony before 1.31.1 does not properly protect state variables in authenticated symmetric NTP associations, which allows remote attackers wi
    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

  • No special conditions are required; it is repeatable.

If successful

Confidentiality
P · data can be read
Integrity
P · data or configuration can be modified
Availability
P · the service can be disrupted
Attack complexity
Low
Confidentiality impact
P
Integrity impact
P
Availability impact
P

Weakness class (CWE)

CWE-119 · Improper Restriction of Operations within the Bounds of a Memory Buffer

CVSS vector

AV:N/AC:L/Au:S/C:P/I:P/A:P

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.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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References

Show all references (4 more)

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

All records