Http4s: DigestAuth nonce map grows unbounded
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 software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | org.http4s:http4s-ember-server_2.12 | < 0.23.35 | 0.23.35 |
| Java / Kotlin (Maven) | org.http4s:http4s-ember-server_2.13 | < 0.23.35, >= 1.0.0-M1, < 1.0.0-M47 | 0.23.35, 1.0.0-M47 |
| Java / Kotlin (Maven) | org.http4s:http4s-ember-server_3 | < 0.23.35, >= 1.0.0-M1, < 1.0.0-M47 | 0.23.35, 1.0.0-M47 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400, CWE-401- Platform
- Java / Kotlin (Maven)
- Package
org.http4s:http4s-ember-server_2.12, org.http4s:http4s-ember-server_2.13, org.http4s:http4s-ember-server_3- Disclosed
- 15.09.2026
- Updated
- 11.10.2026 13:20
Sources and licenses
OSV / GitHub Advisory Database - GHSA-fm4g-76c9-7w69 - CC BY 4.0
Vulnerability history: org.http4s:http4s-ember-server_3
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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