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CVE-2026-87721 – Denial of Service (Query Parser ReDoS) – Gerrit Code Review 2.0.19–3.12.9, 3.13.0–3

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Summary

CVE-2026-87721 is an uncontrolled resource consumption vulnerability (CWE-400/CWE-407/CWE-834) in the ANTLR 3-based search query parser (QueryParser / Query.g) used by Gerrit Code Review. A remote, unauthenticated attacker (or any authenticated user if anonymous read access is disabled) can send a small number of specially crafted search queries to cause CPU exhaustion and permanently pin the HTTP worker thread pool, resulting in a persistent denial of service that requires a server restart to recover. The issue carries a CVSS score of 8.7 (High).

Technical details

  • Root cause: The syntactic predicates in the grammar’s conditionOr and conditionAnd rules recurse through conditionBase without memoization, causing exponential backtracking when parsing certain query strings before any capability or visibility check is performed.
  • Trigger conditions: A search query containing deeply nested parentheses is submitted to any Gerrit query evaluation endpoint.
  • Attack vector: Network-based; queries can be sent via HTTP endpoints (/changes/?q=, /accounts/?q=, /groups/?query=, /projects/?query=, /Documentation/?q=, /changes/{id}/query?expression=) or via SSH (gerrit query). Worker threads do not abort when the client disconnects, so an attacker does not need to keep the connection open.
  • Impact: Because a default httpd.maxThreads configuration is 25, as few as ~25 concurrent malicious requests can pin all available HTTP worker threads, making the Gerrit instance unresponsive to legitimate users until it is restarted.

Affected software

  • Gerrit Code Review 2.0.19 up to (but not including) 3.12.10
  • Gerrit Code Review 3.13.0 up to (but not including) 3.13.9
  • Gerrit Code Review 3.14.0 up to (but not including) 3.14.3

Severity

  • CVSS v4.0 Base Score: 8.7 (High)
  • Vector String: 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

Mitigation and recommended actions

  • Immediate: Upgrade to Gerrit Code Review 3.12.10, 3.13.9, or 3.14.3, or later, which fix the query parser recursion issue.
  • If patching is not immediately possible:
    • Restrict network access to Gerrit’s HTTP and SSH query endpoints to trusted networks or IP ranges where feasible.
    • Consider disabling anonymous read access to reduce the pool of unauthenticated attackers able to submit queries.
    • Monitor HTTP worker thread pool utilization and application logs for spikes in CPU usage or thread exhaustion correlated with unusual/complex search query patterns, and be prepared to restart the service if it becomes unresponsive.

References

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