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CVE-2026-13500 antlr CVE debrief

CVE-2026-13500 is a code injection vulnerability in ANTLR4 up to 4.13.2. The vulnerability affects an unknown function of the file tool/src/org/antlr/v4/codegen/model/OutputFile.java in the Grammar Action Block Handler component. This weakness can be exploited remotely, and a public exploit is available. The vendor, Unknown Vendor, was contacted but did not respond. The CVSS score is 5.5, and the severity is MEDIUM.

Vendor
antlr
Product
ANTLR4
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-28
Original CVE updated
2026-06-28
Advisory published
2026-06-28
Advisory updated
2026-06-28

Who should care

Organizations using ANTLR4 up to version 4.13.2 should be aware of this vulnerability and take necessary actions to mitigate the risk. The vulnerability can be exploited remotely, and a public exploit is available, increasing the urgency for patching. Security teams and developers using ANTLR4 should prioritize patching and monitoring.

Technical summary

The vulnerability is caused by a weakness in the Grammar Action Block Handler component of ANTLR4 up to 4.13.2. The affected function is located in the file tool/src/org/antlr/v4/codegen/model/OutputFile.java. The vulnerability allows for code injection, which can be exploited remotely. The CVSS vector is CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X.

Defensive priority

The vulnerability has a MEDIUM severity and a CVSS score of 5.5. Organizations should prioritize patching and monitoring to mitigate the risk of code injection attacks.

Recommended defensive actions

  • Patch ANTLR4 to version 4.13.2 or later
  • Monitor for suspicious activity related to code injection
  • Review and update security configurations for ANTLR4
  • Implement compensating controls to detect and prevent code injection attacks
  • Verify vendor remediation workflow and exception tracking

Evidence notes

The vulnerability was disclosed on June 28, 2026, and the vendor, Unknown Vendor, was contacted but did not respond. The exploit has been made publicly available, increasing the risk of attacks. The CVE record and NVD detail provide additional information about the vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-13500 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-13500

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-13500 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-13500

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.