libass: Out-of-bounds read and write in wrap_lines_measure

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-61627
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-30 15:16:52 UTC
Updated2026-10-30 19:39:14 UTC
Descriptionlibass 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.

Risk And Classification

Primary CVSS: v4.0 7.3 HIGH from [email protected]

CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.001550000 probability, percentile 0.046110000 (date 2026-11-02)

Problem Types: CWE-125 | CWE-787 | CWE-125 CWE-125: Out-of-bounds Read | CWE-787 CWE-787: Out-of-bounds Write

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7.3HIGHCVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/C...
4.0CNADECLARED7.3HIGHCVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Local
Attack Complexity
High
Attack Requirements
None
Privileges Required
None
User Interaction
Passive
Confidentiality
High
Integrity
High
Availability
High
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Libass Libass affected < 0.17.5 Not specified

References

ReferenceSourceLinkTags
lists.debian.org/debian-lts-announce/2026/09/msg00004.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
github.com/libass/libass/commit/f2ef59755292bc4bb950ef22710e18a5487c399d [email protected] github.com
github.com/libass/libass/releases/tag/0.17.5 [email protected] github.com
github.com/libass/libass/security/advisories/GHSA-pjjp-65r7-ppgm [email protected] github.com
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