Is there a public PoC exploit available for CVE-2026-13502?

Yes, a public proof-of-concept exploit is available for CVE-2026-13502. Prioritise patching immediately. EPSS: 0.1%.

ANTLR4 Maven Plugin CVE-2026-13502

Q: What is the CVSS score of CVE-2026-13502?

CVE-2026-13502 has a CVSS 4.0 base score of 1.1 (Low). CVSS vector: CVSS:4.0/AV:L/AC:H/AT:N/PR:L/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. EPSS exploitation probability: 0.1%.

EUVD-2026-40000 LOW

Time-of-check Time-of-use (TOCTOU) Race Condition (CWE-367)

2026-06-28 VulDB

GHSA-h73j-vjhq-j9vg

Java Information Disclosure Antlr4 Antlr

1.1

CVSS 4.0 · Vendor: VulDB

Severity by source

Vendor (VulDB) PRIMARY

1.1 LOW

CVSS:4.0/AV:L/AC:H/AT:N/PR:L/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

vuln.today AI

4.5 MEDIUM

Local-only race condition requiring low privileges and high complexity; limited impact across all three dimensions with no scope change.

3.1 AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

4.0 AV:L/AC:H/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

Primary rating from Vendor (VulDB).

CVSS VectorVendor: VulDB

Attack Vector

Local

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Lifecycle Timeline

Analysis Generated

Jun 28, 2026 - 15:31 vuln.today

CVSS changed

Jun 28, 2026 - 15:22 NVD

2.0 (LOW) 1.1 (LOW)

DescriptionCVE.org

A flaw has been found in antlr ANTLR4 up to 4.13.2. This affects the function ObjectInputStream.readObject of the file antlr4-maven-plugin/src/main/java/org/antlr/mojo/antlr4/GrammarDependencies.java of the component Maven Plugin. This manipulation causes time-of-check time-of-use. The attack is restricted to local execution. A high degree of complexity is needed for the attack. It is indicated that the exploitability is difficult. The exploit has been published and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

AnalysisAI

Time-of-check time-of-use (TOCTOU) race condition in antlr4-maven-plugin up to version 4.13.2 allows a local low-privileged attacker to manipulate grammar dependency state between validation and consumption in ObjectInputStream.readObject() within GrammarDependencies.java, yielding limited confidentiality, integrity, and availability impact on build artifacts. No public exploit identified at time of analysis is incorrect here - a publicly available exploit exists via a GitHub issue, though KEV listing is absent, indicating no confirmed widespread active exploitation. The CVSS 4.0 score of 1.1 reflects genuine low real-world risk due to local-only access, high attack complexity, and constrained impact scope.

Technical ContextAI

ANTLR4 (Another Tool for Language Recognition, version 4) is a Java-based parser generator widely used in compiler and language tooling projects. The affected component is the antlr4-maven-plugin (CPE: cpe:2.3:a:antlr:antlr4:*:*:*:*:*:*:*:*), which automates grammar compilation during Maven builds. The vulnerable code path is in GrammarDependencies.java, which calls ObjectInputStream.readObject() to deserialize cached grammar dependency data from disk. CWE-367 (Time-Of-Check Time-Of-Use) describes the root cause: the plugin reads a file handle or path reference, validates or checks a property of the object (e.g., file integrity, class type), and then proceeds to use the data - but a race window between check and use allows a concurrent local process to swap or modify the underlying file. Java's ObjectInputStream.readObject() is historically sensitive to the deserialization of unexpected class graphs; in this TOCTOU context, the attacker exploits the gap rather than a pure gadget-chain deserialization flaw. The plugin runs at build time, not production runtime, which significantly constrains the attack surface.

RemediationAI

No vendor-released patch has been identified at time of analysis - the vendor did not respond to coordinated disclosure. Teams using antlr4-maven-plugin should consider pinning to the latest 4.13.2 release and monitoring the upstream ANTLR4 GitHub repository for any subsequent releases that address this issue. As a compensating control, restrict write access to the Maven local repository cache and build working directories so that only the build service account can write to these paths, reducing the feasibility of file substitution during the TOCTOU window. Running Maven builds in isolated, ephemeral containers (e.g., Docker build stages with read-only bind mounts for dependency caches) eliminates the local attacker's ability to race the file operation, though this introduces build infrastructure overhead. Disabling grammar dependency caching in the plugin, if the configuration supports it, would eliminate the ObjectInputStream.readObject() code path entirely, but this may significantly increase incremental build times. Reference the POC at https://github.com/wooyun123/wooyun/issues/7 to understand the race window and validate whether mitigations are effective in your specific build environment.