free5GC AUSF uses non-constant-time authentication comparisons and logs XRES* in 5G-AKA

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-55785
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-28 23:17:07 UTC
Updated2026-08-28 23:17:07 UTC
Descriptionfree5GC is an open-source implementation of the 5G core network. Prior to 1.4.5, the AUSF component performs cryptographic authentication comparisons in internal/sbi/processor/ue_authentication.go with ordinary equality helpers. Auth5gAkaComfirmRequestProcedure compares RES* and XRES* with strings.EqualFold and logs the expected XRES* value at INFO level before comparison. EapAuthComfirmRequestProcedure compares AT_MAC and XMAC with bytes.Equal and evaluates XRES == RES with ordinary string equality. These comparisons can return at mismatch-dependent times, although testing did not demonstrate a practical remote timing oracle because of HTTP/SBI timing noise. The INFO log exposes authentication material to operators, log collectors, sidecars, or processes able to read AUSF logs. This issue is fixed in version 1.4.5.

Risk And Classification

Primary CVSS: v3.1 3.7 LOW from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Problem Types: CWE-208 | CWE-385 | CWE-532 | CWE-208 CWE-208: Observable Timing Discrepancy | CWE-385 CWE-385: Covert Timing Channel | CWE-532 CWE-532: Insertion of Sensitive Information into Log File

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
3.1CNADECLARED3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Free5gc Free5gc affected < 1.4.5 Not specified

References

ReferenceSourceLinkTags
github.com/free5gc/ausf/pull/63 [email protected] github.com
github.com/free5gc/free5gc/security/advisories/GHSA-fp46-6vfw-gc9c [email protected] github.com
github.com/free5gc/ausf/commit/7a5a4aa1ec6cd0e1febebf333911c3104968edf0 [email protected] github.com
github.com/free5gc/ausf/releases/tag/v1.4.5 [email protected] github.com
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