CVE-2026-55785
free5GC AUSF uses non-constant-time authentication comparisons and logs XRES* in 5G-AKA
Impact
free5GC 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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/free5gc/ausf | < 1.4.5 | 1.4.5 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-fp46-6vfw-gc9c
- https://github.com/free5gc/free5gc/security/advisories/GHSA-fp46-6vfw-gc9c
- https://github.com/free5gc/ausf/commit/7a5a4aa1ec6cd0e1febebf333911c3104968edf0
- https://github.com/free5gc/ausf/pull/63
- https://github.com/free5gc/ausf/releases/tag/v1.4.5