CVE-2026-53551

MEDIUMPre-NVD 6.96.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 64% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.9Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.9
EG Score
6.9(medium)
EG Risk
62(Attend)
EG Risk 62/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity69% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
0%
EPSS %ILE
36%
KEV
Not listed

Published

July 31, 2026

Last Modified

August 3, 2026

Advisory Details (6)

Auto-updated Jul 31, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_pr, github_release, github.
github Patch Available🟡 PoC Available

AUSF: null byte injection in supiOrSuci causes HTTP 500 internal service failure · Advisory · free5gc/free5gc · GitHub

https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j
github_release Patch Available

v4.2.2

Patch available: free5gc/free5gc v4.2.2

https://github.com/free5gc/free5gc/releases/tag/v4.2.2
generic

[Bugs]AUSF: null byte injection in supiOrSuci causes HTTP 500 internal service failure · Issue #1048 · free5gc/free5gc · GitHub

https://github.com/free5gc/free5gc/issues/1048
github_release Patch Available

v1.4.5

Patch available: free5gc/ausf v1.4.5

https://github.com/free5gc/ausf/releases/tag/v1.4.5
github_pr

fix: validate supi or suci

Fix merged in free5gc/ausf PR #61 on 2026-05-22 — awaiting tagged release

https://github.com/free5gc/ausf/pull/61
github_commit

commit bfc4a10094db (free5gc/ausf)

Fix landed in free5gc/ausf commit bfc4a10094db — awaiting tagged release

https://github.com/free5gc/ausf/commit/bfc4a10094dbacbd862baa4686829f3fcc06ce1e

Vendor Advisories for CVE-2026-53551(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(2 across 1 ecosystem)
Go(2)
PackageVulnerable rangeFixed inDependents
github.com/free5gc/ausf—1.4.5—
github.com/free5gc/free5gc—4.2.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 38× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-20 22:55 UTCEPSS rescore
  2. 2026-08-19 19:04 UTCEG score recompute
  3. 2026-08-19 17:04 UTCEPSS rescore
  4. 2026-08-18 15:50 UTCEG score recompute
  5. 2026-08-18 13:48 UTCEPSS rescore
  6. 2026-08-17 13:47 UTCEPSS rescore
  7. 2026-08-17 13:04 UTCEG score recompute
  8. 2026-08-16 14:56 UTCEPSS rescore
  9. 2026-08-16 11:35 UTCEG score recompute
  10. 2026-08-16 02:14 UTCEPSS rescore
  11. 2026-08-15 10:07 UTCEG score recompute
  12. 2026-08-15 01:30 UTCEPSS rescore
  13. 2026-08-14 08:38 UTCEG score recompute
  14. 2026-08-13 22:00 UTCEPSS rescore
  15. 2026-08-13 07:09 UTCEG score recompute
  16. 2026-08-12 13:51 UTCEPSS rescore
  17. 2026-08-12 05:38 UTCEG score recompute
  18. 2026-08-11 04:04 UTCEG score recompute
  19. 2026-08-11 00:00 UTCEPSS rescore
  20. 2026-08-10 02:35 UTCEG score recompute
  21. 2026-08-09 13:46 UTCEPSS rescore
  22. 2026-08-09 01:07 UTCEG score recompute
  23. 2026-08-08 16:37 UTCEPSS rescore
  24. 2026-08-07 23:37 UTCEG score recompute
  25. 2026-08-06 22:08 UTCEG score recompute
Show 13 more
  1. 2026-08-06 13:47 UTCEPSS rescore
  2. 2026-08-05 20:40 UTCEG score recompute
  3. 2026-08-05 19:17 UTCEPSS rescore
  4. 2026-08-04 19:11 UTCEG score recompute
  5. 2026-08-04 15:10 UTCEPSS rescore
  6. 2026-08-04 10:39 UTCEPSS rescore
  7. 2026-08-03 17:42 UTCEG score recompute
  8. 2026-08-03 17:13 UTCEG score recompute
  9. 2026-08-03 10:36 UTCEPSS rescore
  10. 2026-08-02 23:19 UTCEG score recompute
  11. 2026-08-02 02:27 UTCEPSS rescore
  12. 2026-07-31 20:21 UTCEG score recompute
  13. 2026-07-31 20:18 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-53551?
CVE-2026-53551 is a medium vulnerability published on July 31, 2026. 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…
When was CVE-2026-53551 disclosed?
CVE-2026-53551 was first published in the National Vulnerability Database on July 31, 2026, with the most recent update on August 3, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-53551 actively exploited?
CVE-2026-53551 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 64.0% of all scored CVEs.
What is the CVSS score of CVE-2026-53551?
CVE-2026-53551 has a CVSS v3 base score of 6.9 (NVD).
How do I remediate CVE-2026-53551?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-53551, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-53551

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