Aegisub executes arbitrary code through automatically loaded Automation scripts

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Aegisub is a cross-platform advanced subtitle editor. From 3.2.0 to 3.4.2, Aegisub automatically loads Automation scripts referenced by `Automation Scripts` metadata in `ASS` subtitle projects without asking whether the user trusts the scripts or their authors. An attacker can distribute a crafted `ASS` file together with a referenced malicious Automation script, and opening the `AS`  file executes arbitrary code with the privileges of the Aegisub process. From 3.4.0 to 3.4.2, inconsistent handling of embedded `NUL` characters between extension validation and filesystem operations additionally allows a crafted `ASS/Lua` polyglot to reference and execute itself as a single-file variant. The vulnerability is fixed in Aegisub 3.5.0.

Source published

9 Oct 2026 20:37:58 UTC

Source modified

14 Oct 2026 02:14:56 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 3.1 · 7.8 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H