# CVE-2026-61627: libass: libass is a portable subtitle renderer for the `ASS`/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format

CVE-2026-61627 is fixed in 2 products on 1 platform, first by libass9 1:0.17.1-2ubuntu0.1~esm1, released July 13, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-61627
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0016
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 13, 2026

## Description

libass is a portable subtitle renderer for the `ASS`/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. Prior to 0.17.5, libass can overread and overwrite the glyph array in `wrap_lines_measure` while rendering malicious `ASS` content. In `wrap modes other than two`, a final line ending with a literal backslash-n sequence and otherwise consisting only of such sequences or spaces can remain after early trimming and make the line-measurement loops overshoot by one glyph. When the total text size exactly matches the allocated glyph-array capacity, the first loop reads an uninitialized 32-bit fixed-point `pos.x` value, although that value is not subsequently used. The second loop writes `pos.x` and `pos.y` beyond the array, zeroing the first and adding an attacker-controllable offset to the second. No actual exploitation beyond possible denial of service is known; broader exploitation is theoretical and constrained by the addresses, limited writes, and ASLR. This issue is fixed in version 0.17.5.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libass Debian 12.15 (bookworm) | 1:0.17.1-1+deb12u1 | [DEBIAN-CVE-2026-61627](https://patchblox.com/security/data/fix/linux/debian-cve-2026-61627.md) | Jul 14, 2026 |
| Linux | libass Debian 13.5 (trixie) | 1:0.17.3-1+deb13u1 | [DEBIAN-CVE-2026-61627](https://patchblox.com/security/data/fix/linux/debian-cve-2026-61627.md) | Jul 14, 2026 |
| Linux | libass Debian 14 | 1:0.17.5-1 | [DEBIAN-CVE-2026-61627](https://patchblox.com/security/data/fix/linux/debian-cve-2026-61627.md) | Jul 14, 2026 |
| Linux | libass9 Ubuntu 24.04.5 LTS (noble) | 1:0.17.1-2ubuntu0.1~esm1 | [libass9 1:0.17.1-2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libass9-1-0.17.1-2ubuntu0.1-esm1.md) | Jul 13, 2026 |
| Linux | libass9 Ubuntu 26.04.1 LTS (resolute) | 1:0.17.4-2ubuntu0.1~esm1 | [libass9 1:0.17.4-2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libass9-1-0.17.4-2ubuntu0.1-esm1.md) | Jul 13, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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