UnratedPublic exploit

Code Injection in ANTLR4 Grammar Action Block Handler

IdentifiersCVE-2026-13500CWE-94

CVE-2026-13500 is a code injection vulnerability affecting antlr ANTLR4 up to and including version 4.13.2. The issue is reported in the Grammar Action Block Handler, specifically involving an unknown function in tool/src/org/antlr/v4/codegen/model/OutputFile.java. According to the provided content, a crafted manipulation of this functionality can result in code injection. The vulnerability is described as remotely exploitable, and public exploit information is available. No additional technical detail about the exact vulnerable function, parsing path, or injection primitive is provided in the supplied content.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can allow an attacker to inject code through the affected Grammar Action Block Handler processing path. Based on the available information, this could result in execution of attacker-controlled code in the context of the vulnerable ANTLR4 code generation workflow or downstream generated output, depending on how the affected component is used. The precise execution context and scope of compromise are not specified in the provided content.

Mitigation

If you can’t patch tonight, do this now.

Until a fixed release is available, limit exposure by preventing untrusted or externally supplied grammar content, action blocks, or related inputs from being processed by vulnerable ANTLR4 code generation workflows. Restrict remote access to any service that accepts such input, isolate build or generation environments, and apply input validation or policy controls to disallow unsafe embedded actions where feasible. Additional mitigation guidance is not available in the provided content.

Remediation

Patch, then assume compromise.

Upgrade ANTLR4 to a version newer than 4.13.2 once a vendor-fixed release is available. Because the vendor reportedly had not responded at the time of disclosure, no specific patched version is identified in the provided content.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

8 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.

8 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

What this page doesn’t show

The version that knows your environment.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity8

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-13500

NVD

nvd.nist.gov/vuln/detail/CVE-2026-13500

MITRE CWE · CWE-94

cwe.mitre.org