CVE-2026-61626

What it is

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 `ReadOrder` 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 `ass_process_chunk`, enabled read-order checking, and later pruning of the malicious events. Read-order checking is enabled by default unless `ass_set_check_readorder` is called with zero; pruning must occur explicitly through `ass_prune_events` or through automatic pruning previously enabled with `ass_configure_prune`. 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.

At a glance

Exploitability

Can be exploited locally on the machine without logging in, but needs a user to act. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-07-10 17:38 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-10-30 15:16 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-11-04 23:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.1% in the next 30 days (EPSS).
• Severity: 7.3 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-10-30 15:16 UTC

Last modified

2026-11-04 23:17 UTC

Exploit probability

0.1% · EPSS, next 30 days

Weakness

CWE-787 · Out-of-bounds write

Record status

Deferred

Attack profile CVSS 4.0 · 7.3

Attack vector

Local

Complexity

High

Attack requirements

None

Privileges needed

None

User interaction

Passive

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-61626.md and follow it. Check whether this project is affected by CVE-2026-61626. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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