CyberSecBulletin
CVE-2026-92705NVD status: Deferred

Aegisub: Improper Neutralization of Null Byte or NUL Character

Published Updated By the CyberSecBulletin desk

CVE-2026-92705 is a high-severity improper neutralization of null byte or NUL character vulnerability in Aegisub from TypesettingTools, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected Aegisub versions: >= 3.2.0, < 3.5.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of Aegisub you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
TypesettingToolsAegisub>= 3.2.0, < 3.5.0Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA (github.com).

Official description

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: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Null Byte or NUL Character

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes NUL characters or null bytes when they are sent to a downstream component.

How developers prevent this class of flaw

  • Developers should anticipate that null characters or null bytes will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
  • Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.

More Improper Neutralization of Null Byte or NUL Character vulnerabilities (CWE-158)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Neutralization of Null Byte or NUL Character vulnerabilities

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