Listen to this Post
The vulnerability exists within the AsyncHttpClient library where the client nonce (cnonce) utilized during HTTP Digest authentication is generated using ThreadLocalRandom rather than a cryptographically secure pseudo-random number generator. According to RFC 7616 section 3.3, the cnonce value must remain completely unpredictable to protect the underlying Digest authentication exchange against chosen-plaintext and credential precomputation attacks. Because ThreadLocalRandom is a fast pseudorandom number generator optimized for concurrent usage rather than cryptographic security, an attacker who is able to observe or influence sufficient generator outputs can reduce the protocol’s expected unpredictability. This deficiency compromises the integrity of the credentials being passed over the network. Other authentication mechanisms like NTLM already correctly implement SecureRandom for their nonces, but Digest omitted this secure implementation, creating an inconsistency that leaves sessions vulnerable to predictability analysis and potential credential compromise if an adversary can correlate state information across multiple authentication requests.
DailyCVE Form:
Platform: AsyncHttpClient Java Library
Version: 3.0.0 to 3.0.11
Vulnerability : Non-cryptographic random source
Severity: Low severity
date: August 9, 2026
Prediction: Already patched
What Undercode Say
The underlying vulnerability stems from initialization parameters in `Realm.Builder` where byte seeding relied on `ThreadLocalRandom.current()` instead of employing a proper instance of SecureRandom.
// Vulnerable implementation snippet using ThreadLocalRandom byte[] bytes = new byte.[bash]; ThreadLocalRandom.current().nextBytes(bytes);
// Secure implementation snippet using SecureRandom SecureRandom secureRandom = new SecureRandom(); byte[] bytes = new byte[bash]; secureRandom.nextBytes(bytes);
Exploit: (Educational Purposes!)
An adversary monitors multiple consecutive HTTP Digest authentication handshakes issued by the vulnerable application client. Because `ThreadLocalRandom` state can potentially be tracked or inferred under specific concurrency conditions, the attacker predicts subsequent cnonce values. Precomputing credential hashes using the forecasted cnonce enables unauthorized authentication or session replay attacks against protected backend endpoints.
Protection: from this CVE
Upgrade the AsyncHttpClient dependency immediately to version 3.0.12 or version 2.16.1 where `Realm.Builder` utilizes `SecureRandom` for generating client nonces.
Impact:
Allows potential chosen-plaintext attacks and credential precomputation vectors against HTTP Digest authentication exchanges if an attacker successfully predicts the weak pseudorandom cnonce values.
🎯Let’s Practice Exploiting & Learn Patching For Free:
🎓 Live Courses & Certifications:
Join Undercode Academy for Verified Certifications
🚀 Request a Custom Project:
Secure, high-velocity infrastructure and disruptive technological engineering. Contact our engineering team for high-tier development and proprietary systems:
[email protected]
💎 Smart Architecture | 🛡️ Secure by Design | ⭐ Trusted by Thousands
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
