CVE-2025-40918

Authen::SASL::Perl::DIGEST_MD5 versions 2.04 through 2.1800 for Perl generates the cnonce insecurely. The cnonce (client nonce) is generated from an MD5 hash of the PID, the epoch time and the built-in rand function. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. The built-in rand function is unsuitable for cryptographic usage. According to RFC 2831, The cnonce-value is an opaque quoted string value provided by the client and used by both client and server to avoid chosen plaintext attacks, and to provide mutual authentication. The security of the implementation depends on a good choice. It is RECOMMENDED that it contain at least 64 bits of entropy.

Read the notes from the security team

Why is this CVE low priority?

Vulnerability in obsolete SASL mechanism

Learn more about Ubuntu priority

Mitigation

The DIGEST-MD5 SASL mechanism is insecure and has been marked as OBSOLETE since 2011. We recommend using a more recent and secure mechanism in production environments.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
libauthen-sasl-perl	25.04 plucky	Needs evaluation
	24.04 LTS noble	Needs evaluation
	22.04 LTS jammy	Needs evaluation
	20.04 LTS focal	Needs evaluation
	18.04 LTS bionic	Needs evaluation
	16.04 LTS xenial	Needs evaluation
	14.04 LTS trusty	Needs evaluation

Notes

mdeslaur

The upstream fix for this issue would require introducing a new dependency on the libcrypt-urandom-perl package, which is in universe. The DIGEST-MD5 mechanism has been marked as OBSOLETE in 2011 by RFC6331, is insecure, and should not be used in production environments. Since this mechanism is insecure, with or without the fix for this vulnerability, marking proority as "low."

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
libauthen-sasl-perl	Upstream: https://security.metacpan.org/patches/A/Authen-SASL/2.1800/CVE-2025-40918-r1.patch Upstream: https://github.com/gbarr/perl-authen-sasl/pull/22

Severity score breakdown

Parameter	Value
Base score	6.5 · Medium
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	Low
Integrity impact	Low
Availability impact	None
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N