GHSA-fm4g-76c9-7w69 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in org.http4s:http4s-ember-server_2.12. O3 Security confirms whether GHSA-fm4g-76c9-7w69 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Http4s: DigestAuth nonce map grows unbounded
Real-World Exposure
org.http4s:http4s-ember-server_2.12☕org.http4s:http4s-ember-server_2.13☕org.http4s:http4s-ember-server_3☕org.http4s:http4s-ember-server_2.13☕org.http4s:http4s-ember-server_3Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
The DigestAuth server middleware's stale-nonce cleanup uses an inverted comparison: it removes fresh nonces and stops at the first stale one. Because a new nonce is created for every unauthenticated challenge, an attacker can drive the nonce map to grow without bound until the JVM runs out of heap.
Impact
Unauthenticated remote denial of service (gradual heap exhaustion / OOM) against any service using DigestAuth. The leak is persistent.
Preconditions
- Application uses
DigestAuthon at least one route.
Workarounds
- Front the DigestAuth protected routes with a rate limiter to slow the leak.
- Restart periodically.
Fixes
- The eviction logic is corrected.
- A max cache size of 1000000 is imposed to protected against a burst between evictions. This limit is not yet configurable.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.http4s:http4s-ember-server_2.12 | all versions | 0.23.35 |
| ☕Maven | org.http4s:http4s-ember-server_2.13 | all versions | 0.23.35 |
| ☕Maven | org.http4s:http4s-ember-server_3 | all versions | 0.23.35 |
| ☕Maven | org.http4s:http4s-ember-server_2.13 | ≥ 1.0.0-M1&&< 1.0.0-M47 | 1.0.0-M47 |
| ☕Maven | org.http4s:http4s-ember-server_3 | ≥ 1.0.0-M1&&< 1.0.0-M47 | 1.0.0-M47 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-ember-server_2.12. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.http4s:http4s-ember-server_2.12 to 0.23.35 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fm4g-76c9-7w69 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-fm4g-76c9-7w69 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-fm4g-76c9-7w69. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-fm4g-76c9-7w69 in your dependencies?
O3 detects GHSA-fm4g-76c9-7w69 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.