{"id":"CVE-2026-61626","published":"2026-10-30T15:16:52.500","lastModified":"2026-10-30T19:39:14.897","description":"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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":["CWE-787"],"vendors":[],"products":[],"references":[{"url":"https://github.com/libass/libass/commit/23da65a130bb8c5b2cf0c7df0dd7d424607f98f1","tags":[]},{"url":"https://github.com/libass/libass/releases/tag/0.17.5","tags":[]},{"url":"https://github.com/libass/libass/security/advisories/GHSA-5gf7-wjfm-vmvm","tags":[]}],"exploitRefs":[{"url":"https://github.com/libass/libass/commit/23da65a130bb8c5b2cf0c7df0dd7d424607f98f1","tags":[]},{"url":"https://github.com/libass/libass/releases/tag/0.17.5","tags":[]},{"url":"https://github.com/libass/libass/security/advisories/GHSA-5gf7-wjfm-vmvm","tags":[]}],"hasPoc":true,"ai":null}