CVE-2021-42697
HIGHCVE-2021-42697 is a high-severity (CVSS 7.5) CWE-674 vulnerability in com.typesafe.akka:akka-http-core_2.13.0-RC3. 2 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-42697 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Uncontrolled Recursion in Akka HTTP
Real-World Exposure
com.typesafe.akka:akka-http-core_2.13.0-RC3☕com.typesafe.akka:akka-http-core_2.13.0-RC2☕com.typesafe.akka:akka-http-core_2.13.0-M5☕com.typesafe.akka:aakka-http-core_2.13.0-M3☕com.typesafe.akka:akka-http-core_2.13☕com.typesafe.akka:akka-http-core_2.13☕com.typesafe.akka:akka-http-core_2.12☕com.typesafe.akka:akka-http-core_2.12+1 moreReal-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
Akka HTTP 10.1.x before 10.1.15 and 10.2.x before 10.2.7 can encounter stack exhaustion while parsing HTTP headers, which allows a remote attacker to conduct a Denial of Service attack by sending a User-Agent header with deeply nested comments.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | com.typesafe.akka:akka-http-core_2.13.0-RC3 | ≥ 10.1.0 | No fix |
| ☕Maven | com.typesafe.akka:akka-http-core_2.13.0-RC2 | ≥ 10.1.0 | No fix |
| ☕Maven | com.typesafe.akka:akka-http-core_2.13.0-M5 | ≥ 10.1.0 | No fix |
| ☕Maven | com.typesafe.akka:aakka-http-core_2.13.0-M3 | ≥ 10.1.0 | No fix |
| ☕Maven | com.typesafe.akka:akka-http-core_2.13 | ≥ 10.1.0&&< 10.1.15 | 10.1.15 |
| ☕Maven | com.typesafe.akka:akka-http-core_2.13 | ≥ 10.2.0-M1&&< 10.2.7 | 10.2.7 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Akka HTTP 10.1.14 - Denial of Service
by cxosmo · May 11, 2022
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.typesafe.akka:akka-http-core_2.13.0-RC3. 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
No patched version of com.typesafe.akka:akka-http-core_2.13.0-RC3 has shipped for CVE-2021-42697 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
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 CVE-2021-42697 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 CVE-2021-42697. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-42697 in your dependencies?
O3 detects CVE-2021-42697 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.