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Digest authentication cnonce generated with a non-cryptographic random source

Low
hyperxpro published GHSA-mfj3-87qq-382v Aug 9, 2026

Package

maven org.asynchttpclient:async-http-client (Maven)

Affected versions

>= 3.0.0, <= 3.0.11
>= 2.0.0, <= 2.16.0

Patched versions

3.0.12
2.16.1

Description

Impact

The client nonce used in HTTP Digest authentication was generated from ThreadLocalRandom, a fast but non-cryptographic pseudorandom number generator. RFC 7616 section 3.3 requires the cnonce to be unpredictable, since it is part of what protects the Digest exchange against chosen-plaintext and precomputation attacks on the credentials. An attacker able to observe or influence enough of the generator's output could reduce the unpredictability the protocol depends on. NTLM (and, on the 3.x line, SCRAM) in this client already use SecureRandom for their own nonces; Digest did not.

Affected versions

  • 3.x: up to and including 3.0.11
  • 2.x: up to and including 2.16.0

Patches

Fixed in 3.0.12 on the 3.x line and in 2.16.1 on the 2.x line. The cnonce is now generated with SecureRandom, matching the other authentication schemes in the client.

Workarounds

None available from application code.

Details

Realm.Builder's cnonce generation seeded its bytes from ThreadLocalRandom.current() rather than a SecureRandom instance.

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CVE ID

No known CVE

Weaknesses

Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong. Learn more on MITRE.