# CVE-2026-55785: free5GC AUSF non-constant-time authentication comparison and sensitive logging

Source: https://junglewise.ai/threats/cve-2026-55785-free5gc-ausf-non-constant-time-authentication-comparison-and  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-28. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-55785 · Severity: low · CVSS 3.7 · Published 2026-08-28

free5GC's AUSF (Authentication Server Function) component handles 5G network user authentication using cryptographic protocols. The component compares authentication response values using non-constant-time comparison functions and logs sensitive authentication credentials (XRES*) to application logs. While timing attacks over the network were not practically demonstrated in testing, the direct exposure of authentication material in logs creates a risk if logs are accessible to operators, infrastructure systems, or log aggregation platforms.

Technologies: [github.com/free5gc/ausf (Go)](https://junglewise.ai/threats/technologies/github-com-free5gc-ausf). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-55785 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55785 being exploited in the wild.

**How severe is CVE-2026-55785?** Low severity, with a CVSS score of 3.7, published 28 August 2026.

**Which products and versions are affected?** github.com/free5gc/ausf (Go) < 1.4.5, SEMVER:introduced=0,fixed=1.4.5.

**Is there a fix for CVE-2026-55785?** Yes. github.com/free5gc/ausf (Go): upgrade to 1.4.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55785 attacked?** It is attacked over the network or with local access.

**Am I affected by CVE-2026-55785?** Check whether you run github.com/free5gc/ausf (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/free5gc/ausf (Go): upgrade to 1.4.5 or later

  ```sh
  go get github.com/free5gc/ausf@v1.4.5
  ```


## Technical details

The vulnerability consists of two issues in `internal/sbi/processor/ue_authentication.go`. First, the 5G-AKA authentication confirmation path uses `strings.EqualFold()` to compare RES* and XRES* values—a non-constant-time string comparison that may return early on mismatch. More critically, XRES* (the expected authentication response) is logged at INFO level immediately before comparison, exposing authentication material to any process or system with log access. Second, the EAP-AKA' confirmation path uses `bytes.Equal()` and string `==` comparison for MAC and response values instead of `crypto/subtle.ConstantTimeCompare()`. Lab testing confirmed that timing signal at the comparator level is masked by HTTP/SBI network noise, making remote timing attacks impractical. However, local CPU benchmarks show the non-constant-time behavior is real (0.31 ns delta), and the logging of XRES* is directly observable and exploitable. Fixed in v1.4.5 with constant-time comparisons and removal of sensitive values from logs.

## Affected products

- github.com/free5gc/ausf (Go) < 1.4.5, SEMVER:introduced=0,fixed=1.4.5

## Identifiers

- CVE-2026-55785
- GHSA-fp46-6vfw-gc9c
- GO-2026-6328

## Timeline

- 2026-06-22: disclosed: GitHub Advisory published
- 2026-06-22: patched: v1.4.5 released with fix
- 2026-08-28: advisory

## References

- [https://api.github.com/users/jaimealruiz](https://api.github.com/users/jaimealruiz)
- [https://github.com/jaimealruiz](https://github.com/jaimealruiz)
- [https://api.github.com/users/jaimealruiz/gists%7B/gist_id%7D](https://api.github.com/users/jaimealruiz/gists%7B/gist_id%7D)
- [https://api.github.com/users/jaimealruiz/repos](https://api.github.com/users/jaimealruiz/repos)
- [https://avatars.githubusercontent.com/u/124803932?v=4](https://avatars.githubusercontent.com/u/124803932?v=4)
- [https://api.github.com/users/jaimealruiz/events%7B/privacy%7D](https://api.github.com/users/jaimealruiz/events%7B/privacy%7D)

## Related threats

- [free5GC AUSF authentication context race condition](https://junglewise.ai/threats/cve-2026-55784-free5gc-ausf-authentication-context-race-condition)
- [free5gc AUSF improper input validation in supiOrSuci field](https://junglewise.ai/threats/cve-2026-53551-free5gc-ausf-improper-input-validation-in-supiorsuci-field)
- [GO-2026-4754 - free5GC AUSF UE Authentication Panic on Nil SuciSupiMap Interface Conversion in github.com/free5gc/ausf](https://junglewise.ai/threats/cve-2026-33063-free5gc-ausf-ue-authentication-panic-on-nil-sucisupimap-interface)