CVE-2026-129483

Cyrus SASL through 2.1.28 SRP Authentication Bypass via plugins/srp.c

Published Nov 15, 2026 CVSS 4.0 · 9.3 Critical EPSS n/a KEV · Not listed

Description

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.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

cyrusimap

cyrus-sasl

unaffected

Version	Status	Constraints
`0`	affected	≤ 2.1.28

No data.

No data available yet.

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

No advisories available

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact High

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://gist.github.com/afldl/18d15d3f5a1df99411e35000c7de80db
https://github.com/cyrusimap/cyrus-sasl/blob/cyrus-sasl-2.1.28/plugins/srp.c#L2046-L2050
https://github.com/cyrusimap/cyrus-sasl/commit/fb3724f43dc50247ff2bf02135457d6d77031654
https://github.com/cyrusimap/cyrus-sasl/issues/896
https://seclists.org/oss-sec/2026/q4/122
https://www.vulncheck.com/advisories/cyrus-sasl-through-2.1.28-srp-authentication-bypass-via-plugins-srp-c

History

Nov 15, 2026 2:00 PM Description updated. Title updated. First appearance in the feed. Weaknesses updated. Affected versions updated. Affected vendors updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Description		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.
Title		Cyrus SASL through 2.1.28 SRP Authentication Bypass via plugins/srp.c
First Time appeared		Cyrusimap Cyrusimap cyrus-sasl
Weaknesses		CWE-287
CPEs		cpe:2.3:a:cyrusimap:cyrus-sasl::::::::
Vendors & Products		Cyrusimap Cyrusimap cyrus-sasl
References		https://gist.github.com/afldl/18d15d3f5a1df99411e35000c7de80db https://github.com/cyrusimap/cyrus-sasl/blob/cyrus-sasl-2.1.28/plugins/srp.c#L2046-L2050 https://github.com/cyrusimap/cyrus-sasl/commit/fb3724f43dc50247ff2bf02135457d6d77031654 https://github.com/cyrusimap/cyrus-sasl/issues/896 https://seclists.org/oss-sec/2026/q4/122 https://www.vulncheck.com/advisories/cyrus-sasl-through-2.1.28-srp-authentication-bypass-via-plugins-srp-c
Metrics		cvssV3_1 `{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}` cvssV4_0 `{'score': 9.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'}`