free5GC AUSF uses non-constant-time authentication comparisons and logs XRES* in 5G-AKA (CVE-2026-55785) | HOL Guard CVE

Low · CVSS 3.7CVE-2026-55785GHSA-FP46-6VFW-GC9C

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

Answer in brief

CVE-2026-55785 records a Low severity (CVSS 3.7) vulnerability in free5GC AUSF uses non-constant-time authentication comparisons and logs XRES* in 5G-AKA. The current sources do not mark it as known exploited. The current feed maps free5gc/free5gc (generic), github.com/free5gc/ausf (go). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 28, 2026Updated Aug 28, 2026Source checked Aug 28, 2026First seen by HOL Aug 28, 2026Material review Aug 28, 2026

Upstream Advisory

Key facts

Risk: Low · CVSS 3.7
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 3.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps free5gc/free5gc (generic), github.com/free5gc/ausf (go). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
free5gc/free5gcgeneric	< 1.4.5	Not reported
github.com/free5gc/ausfgo	<1.4.5	1.4.5

Recommended response

Check inventory. Check lockfiles and deployed manifests for free5gc/free5gc, github.com/free5gc/ausf.
Review the reported fix. Update github.com/free5gc/ausf to 1.4.5 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 28, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.