by Kastro
Paper/Archive/CVE-2026-129483

CVE-2026-129483

cyrusimap cyrus-sasl — Cyrus SASL through 2.1.28 SRP Authentication Bypass via plugins/srp.c

CVSS 9.3
critical.is priorityof 100
28
CVSS 9.3 (CNA)9.3 / 10 × 3027.9Not in CISA KEV+300.0No EPSS score.000 × 200.0No public exploit+100.0SSVC exploitation: unknown+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
cyrus-sasl≤ 2.1.28–CNA

Scores by source

VulnCheck (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
VulnCheck (CNA)9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References

refgithub.com/cyrusimap/cyrus-sasl/issues/896refseclists.org/oss-sec/2026/q4/122exploitgist.github.com/afldl/18d15d3f5a1df99411e35000c7de80dbpatchgithub.com/cyrusimap/cyrus-sasl/commit/fb3724f43dc50247ff2bf02135457d6d77031654writeupgithub.com/cyrusimap/cyrus-sasl/blob/cyrus-sasl-2.1.28/plugins/srp.c#L2046-L2050writeupvulncheck.com/advisories/cyrus-sasl-through-2.1.28-srp-authentication-bypass-via-plugins-srp-c