# CVE-2026-13502: antlr ANTLR4 Maven Plugin GrammarDependencies.java ObjectInputStream.readObject toctou

> A time-of-check time-of-use race condition in the ANTLR4 Maven Plugin allows local attackers to potentially execute arbitrary code via deserialization.

- **Severity:** Low 2.0 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Jun 2026
- **Updated:** 29 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-13502, GHSA-h73j-vjhq-j9vg, UBUNTU-CVE-2026-13502

## What is CVE-2026-13502?

CVE-2026-13502 is a low-severity vulnerability in ANTLR4, published on 28 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-13502?


## How do I fix CVE-2026-13502?

No fix published yet.

## Is CVE-2026-13502 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-13502 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-13502 and fix it if it is affected.

What it is: CVE-2026-13502 is a low-severity vulnerability in ANTLR4, published on 28 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-13502 exists.

Affected product: ANTLR4. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-13502/ (Markdown: https://insights.sbomify.com/CVE-2026-13502/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-13502
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-13502
- OSV: https://osv.dev/vulnerability/CVE-2026-13502

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-13502/
Summaries are generated and may contain mistakes; the official description above is the record.