Is CVE-2026-13503 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-13503 being exploited in the wild.

How severe is CVE-2026-13503?

Medium severity, with a CVSS score of 5.3, published 28 June 2026.

Is there a fix for CVE-2026-13503?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-13503 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-13503?

Check whether you run ANTLR4 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-13503: antlr ANTLR4 path traversal in TokenVocabParser

CVE-2026-13503 · Severity: medium · CVSS 5.3 · Published 2026-06-28

ANTLR4 is a widely used tool for processing structured text and programming languages. A security flaw in its grammar handling component allows an attacker to potentially read sensitive files from the system where the tool is running. This could lead to the exposure of configuration data or other private information if the tool processes untrusted grammar files.

Technologies: ANTLR4. Vendors: ANTLR.

Quick answers

Is CVE-2026-13503 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-13503 being exploited in the wild.
How severe is CVE-2026-13503?: Medium severity, with a CVSS score of 5.3, published 28 June 2026.
Which products and versions are affected?: ANTLR4 up to 4.13.2.
Is there a fix for CVE-2026-13503?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-13503 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-13503?: Check whether you run ANTLR4 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A path traversal vulnerability (CWE-22) exists in ANTLR4 up to version 4.13.2 within the TokenVocabParser.java component. The issue is located in the getImportedVocabFile function of the tokenVocab Grammar Option Handler. By providing a specially crafted grammar file, a remote attacker can bypass directory restrictions to read arbitrary files on the host system. The exploit is currently public, and as of the advisory date, the vendor has not responded to disclosure attempts.

Affected products

antlr ANTLR4 up to 4.13.2

Timeline

2026-06-28: advisory: NVD publication date
2026-06-28: disclosed: Public exploit available via GitHub issue

References

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