CVE-2026-13500
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceCode injection vulnerability in ANTLR4's Grammar Action Block Handler (OutputFile.java) allows remote attackers to inject malicious code through manipulated grammar files. The vulnerability affects all versions up to 4.13.2 and stems from insufficient input handling in the code generation process.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify ANTLR4 installation and versionRun 'antlr4 --version' or inspect the antlr-4.x-complete.jar filename in your classpath. Check build configuration files (pom.xml, build.gradle) for antlr4 dependencies.Affected if The installed version is 4.13.2 or earlier, or version cannot be determined and ANTLR4 is present.
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Locate grammar file processing workflowsSearch for .g4 grammar files in your project or system. Identify code or scripts that invoke ANTLR4 to generate parsers from these grammar files.Affected if Grammar files from untrusted or external sources are being processed by ANTLR4.
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Check if custom grammar action blocks are usedInspect .g4 grammar files for action blocks enclosed in braces within grammar rules (e.g., 'ruleName { customCode }'). Review any generated parser code for injected content.Affected if Grammar files contain action blocks that result in code generation into OutputFile.java-derived output.
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Audit code generation output locationsReview generated Java source files in the output directory. Inspect OutputFile.java or similar generated files for unexpected or suspicious code patterns.Affected if Generated source files contain code that was not authored in the original grammar file.
You are affected if ANTLR4 version 4.13.2 or earlier is installed AND your system processes grammar files, especially those from untrusted sources or containing action blocks that generate code into output files.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpdate ANTLR4 to a version beyond 4.13.2 when available; if no patched version exists, implement strict validation of grammar files before processing and consider network isolation of systems parsing untrusted grammars.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-13500 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-13500 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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