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Vulnerabilities

Vulnerability · CVE-2026-61626

libass: Out-of-bounds bit clears for negative Matroska ReadOrder values

Published Oct 30, 2026 · catalog updated Oct 31, 2026 · libass: Out-of-bounds bit clears

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-61626. EPSS is 0.12%. Act only if a listed version of libass: Out-of-bounds bit clears is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (libass: Out-of-bounds bit clears).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.12%
Remediation
Advisory link
Affected products
Debian:14 libass · vendor libass libass

libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. From 0.17.4 until 0.17.5, libass event pruning does not guard negative Matroska values, allowing an attacker to clear arbitrarily many bits to zero at attacker-controlled positions near the NULL pointer. Exploitation requires a malicious Matroska stream loaded through , enabled read-order checking, and later pruning of the malicious events. Read-order checking is enabled by default unless is called with zero; pruning must occur explicitly through or through automatic pruning previously enabled with . On common systems with arithmetic right shift, 32-bit int values, the upper address region reserved to the kernel, and matching binary/kernel architecture, the expected consequence is denial of service. More extensive exploitation on uncommon systems is theoretical and strongly constrained by the target addresses, bit-clearing-only mutation, and ASLR. This issue is fixed in version 0.17.5.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Debian:14 libass0 → 1:0.17.5-1
  • vendor libass libassversion unspecified

How to fix CVE-2026-61626

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-61626. EPSS is 0.12%. Act only if a listed version of libass: Out-of-bounds bit clears is installed.

Which versions are affected?

Compare what you have installed with 0 → 1:0.17.5-1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-787: Out-of-bounds Write. EPSS 0.12%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Debian security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 30, 2026 · Trivy Vulnerability DB

    Detected

  2. Oct 30, 2026 · Trivy Vulnerability DB

    Fix available

    libass fixed in 1:0.17.5-1

  3. Oct 30, 2026 · Trivy Vulnerability DB

    Fix available

    libass fixed in 1:0.17.5-1

  4. Oct 30, 2026 · Trivy Vulnerability DB

    Updated

    The description or metadata changed.

  5. Oct 31, 2026 · Trivy Vulnerability DB

    Updated

    libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. From 0.17.4 until 0.17.5, libass event pruning does not guard negative Matroska values, allowing an attacker to clear arbitrarily many bits to zero at attacker-controlled positions near the NULL pointer. Exploitation requires a malicious Matroska stream loaded through , enabled read

Sources

  • CVE.orgVulnerability recordCVE-2026-61626

    libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. From 0.17.4 until 0.17.5, libass event pruning does not guard negative Matroska values, allowing an attacker to clear arbitrarily many bits to zero at attacker-con

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-61626

    30-day exploitation probability 0.12%

    first.org
  • Trivy Vulnerability DBPackage advisoryDEBIAN-CVE-2026-61626

    libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. From 0.17.4 until 0.17.5, libass event pruning does not guard negative Matroska values, allowing an attacker to clear arbitrarily many bits to zero at attacker-con

    osv.dev

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSOct 31, 2026
  • Trivy Vulnerability DBOct 31, 2026
  • CVE.orgOct 30, 2026