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.

A flaw was found in ANTLR4. A remote attacker could exploit a weakness within the Grammar Action Block Handler component by executing a manipulation. This vulnerability allows for code injection, which can lead to the execution of arbitrary code on the affected system.

This is an Important vulnerability. A remote code injection flaw exists in the ANTLR4 Grammar Action Block Handler, which could allow an unauthenticated attacker to execute arbitrary code. The ability for remote exploitation and the public availability of exploit details elevate the risk, making this a critical concern for Red Hat products that incorporate ANTLR4 and process untrusted input. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Red Hat Enterprise Linux 8 Affected grafana https://www.cve.org/CVERecord?id=CVE-2026-13500 https://nvd.nist.gov/vuln/detail/CVE-2026-13500 https://github.com/wooyun123/wooyun/issues/4 https://vuldb.com/cve/CVE-2026-13500 https://vuldb.com/submit/838568 https://vuldb.com/vuln/374495 https://vuldb.com/vuln/374495/cti