CVE-2026-13500 antlr ANTLR4 Grammar Action Block OutputFile.java code injection
Remote attackers can execute arbitrary code via manipulated grammar action blocks in the ANTLR4 parser generator library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-13500?
CVE-2026-13500 is a medium-severity code injection vulnerability in ANTLR4, published on 28 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A weakness has been identified in antlr ANTLR4 up to 4.13.2. Affected is an unknown function of the file tool/src/org/antlr/v4/codegen/model/OutputFile.java of the component Grammar Action Block Handler. Executing a manipulation can lead to code injection. The attack may be launched remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.
Which versions are affected by CVE-2026-13500?
How do I fix CVE-2026-13500?
No fix has been published for CVE-2026-13500 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-13500 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-13500 exists.
Sources
Also known as DEBIAN-CVE-2026-13500, GHSA-m64j-m5c8-f58p, UBUNTU-CVE-2026-13500.