CVE-2026-53551
free5GC AUSF: null byte injection in supiOrSuci causes HTTP 500 internal service failure
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
free5GC is an open-source implementation of the 5G core network. Prior to 1.4.5, the free5GC AUSF (Authentication Server Function) does not validate the supiOrSuci field in UE authentication requests. Null bytes (\x00) and other control characters pass through JSON parsing unchanged and are forwarded to the UDM in an unescaped URL path. This causes Go's net/url.Parse() to fail, returning HTTP 500 "System failure" and leaking internal stack traces. An unauthenticated attacker can trigger this at scale causing denial of service for all subscribers attempting authentication through the affected AUSF. This vulnerability is fixed in 1.4.5.
Public exploit
A reference of the record is tagged as an exploit or proof of concept: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: a proof of concept is public.
- https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j (opens in a new tab)x_refsource_CONFIRMexploit
Timeline
ID reserved
By GitHub_M
- 52 days later
· 52 days later
Published
- 3 days later
· 3 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 4.0 | Medium6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N |
| NVDNVD · Deferred | 4.0 | Medium6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.74% · top 45% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.9.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/free5gc/ausfGHSA-qj55-47fp-p62j (opens in a new tab)
- Gogithub.com/free5gc/free5gcGHSA-qj55-47fp-p62j (opens in a new tab)
References (6)
- https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/free5gc/free5gc/issues/1048 (opens in a new tab)x_refsource_MISC
- https://github.com/free5gc/ausf/pull/61 (opens in a new tab)x_refsource_MISC
- https://github.com/free5gc/ausf/commit/bfc4a10094dbacbd862baa4686829f3fcc06ce1e (opens in a new tab)x_refsource_MISC
- https://github.com/free5gc/ausf/releases/tag/v1.4.5 (opens in a new tab)x_refsource_MISC
- https://github.com/free5gc/free5gc/releases/tag/v4.2.2 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-qj55-47fp-p62j (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-53551)Record last updated .