CyrusIMAP Cyrus SASL up to 2.1.28 SRP Server Mechanism srp_server_mech_step2 improper authentication

Summaryinfo

A vulnerability categorized as critical has been discovered in CyrusIMAP Cyrus SASL up to 2.1.28. This affects the function srp_server_mech_step2 of the component SRP Server Mechanism. Executing a manipulation can lead to improper authentication. The identification of this vulnerability is CVE-2026-129483. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability has been found in CyrusIMAP Cyrus SASL up to 2.1.28 and classified as critical. This vulnerability affects the function srp_server_mech_step2 of the component SRP Server Mechanism. The manipulation with an unknown input leads to a improper authentication vulnerability. The CWE definition for the vulnerability is CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Cyrus SASL through 2.1.28 contains an authentication bypass vulnerability in the SRP server mechanism because srp_server_mech_step2 does not reject client public values A that are multiples of N. Unauthenticated network clients can send A equal to N to force a zero shared secret, authenticating as any existing user without the password and learning session keys.

The advisory is available at github.com. This vulnerability was named CVE-2026-129483 since 11/15/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 11/15/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• CyrusIMAP

Name

• Cyrus SASL

Version

• 2.1.0
• 2.1.1
• 2.1.2
• 2.1.3
• 2.1.4
• 2.1.5
• 2.1.6
• 2.1.7
• 2.1.8
• 2.1.9
• 2.1.10
• 2.1.11
• 2.1.12
• 2.1.13
• 2.1.14
• 2.1.15
• 2.1.16
• 2.1.17
• 2.1.18
• 2.1.19
• 2.1.20
• 2.1.21
• 2.1.22
• 2.1.23
• 2.1.24
• 2.1.25
• 2.1.26
• 2.1.27
• 2.1.28

CPE 2.3info

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CPE 2.2info

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