CVE-2026-87721 Denial of Service via Exponential Backtracking in ANTLR Search Query Parser in Gerrit Code Review
Unauthenticated attackers can cause persistent denial of service in Gerrit Code Review by sending crafted search queries that exhaust CPU and worker threads.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-87721?
CVE-2026-87721 is a high-severity denial of service vulnerability in Gerrit, published on 24 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-87721?
How do I fix CVE-2026-87721?
No fix has been published for CVE-2026-87721 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-87721 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87721 exists.
Sources
Also known as GHSA-q3rp-qmhw-57f7.