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: 0.7% (52nd percentile of EPSS-scored CVEs). 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: 0.7%CVSS: 6.9Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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
6.9MEDIUMmedium confidence
EG Risk
62
EG Risk 62/100CISA SSVC

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%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.7%
EPSS %ILE
52nd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

July 31, 2026

Last Modified

September 8, 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 rangeFix by version rangeDependents
github.com/free5gc/ausf—
  • every version up to 1.4.5: fixed in 1.4.5
—
github.com/free5gc/free5gc—
  • every version up to 4.2.2: fixed in 4.2.2
  • every version up to 4.2.2+incompatible: fixed in 4.2.2+incompatible
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 41× 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.

Showing the most recent 100 of 102 total refreshes for this CVE.

  1. 2026-10-04 23:22 UTCEPSS rescore
  2. 2026-10-04 06:28 UTCEG score recompute
  3. 2026-10-03 14:26 UTCEPSS rescore
  4. 2026-10-02 17:56 UTCEPSS rescore
  5. 2026-10-02 16:48 UTCEG score recompute
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  8. 2026-09-30 15:03 UTCEPSS rescore
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  10. 2026-09-29 06:49 UTCEG score recompute
  11. 2026-09-28 13:51 UTCEPSS rescore
  12. 2026-09-27 18:38 UTCEG score recompute
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  16. 2026-09-24 10:52 UTCEG score recompute
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  24. 2026-09-18 08:38 UTCEG score recompute
  25. 2026-09-17 07:03 UTCEG score recompute
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  1. 2026-09-16 14:08 UTCEPSS rescore
  2. 2026-09-16 05:27 UTCEG score recompute
  3. 2026-09-16 05:15 UTCEPSS rescore
  4. 2026-09-14 09:24 UTCEG score recompute
  5. 2026-09-13 16:47 UTCEPSS rescore
  6. 2026-09-13 07:56 UTCEG score recompute
  7. 2026-09-12 06:27 UTCEG score recompute
  8. 2026-09-11 14:53 UTCEPSS rescore
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  20. 2026-09-02 14:12 UTCEPSS rescore
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  22. 2026-09-01 13:54 UTCEPSS rescore
  23. 2026-09-01 04:40 UTCEPSS rescore
  24. 2026-08-30 23:47 UTCEG score recompute
  25. 2026-08-30 19:17 UTCEPSS rescore
  26. 2026-08-30 01:22 UTCEPSS rescore
  27. 2026-08-29 22:18 UTCEG score recompute
  28. 2026-08-28 21:41 UTCEPSS rescore
  29. 2026-08-27 14:25 UTCEPSS rescore
  30. 2026-08-27 08:49 UTCEG score recompute
  31. 2026-08-26 14:46 UTCEPSS rescore
  32. 2026-08-26 03:58 UTCEG score recompute
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  35. 2026-08-24 01:00 UTCEG score recompute
  36. 2026-08-23 00:19 UTCEPSS rescore
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  38. 2026-08-21 23:49 UTCEPSS rescore
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  40. 2026-08-20 22:55 UTCEPSS rescore
  41. 2026-08-19 19:04 UTCEG score recompute
  42. 2026-08-19 17:04 UTCEPSS rescore
  43. 2026-08-18 15:50 UTCEG score recompute
  44. 2026-08-18 13:48 UTCEPSS rescore
  45. 2026-08-17 13:47 UTCEPSS rescore
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  47. 2026-08-16 14:56 UTCEPSS rescore
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  55. 2026-08-12 13:51 UTCEPSS rescore
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  69. 2026-08-04 15:10 UTCEPSS rescore
  70. 2026-08-04 10:39 UTCEPSS rescore
  71. 2026-08-03 17:42 UTCEG score recompute
  72. 2026-08-03 17:13 UTCEG score recompute
  73. 2026-08-03 10:36 UTCEPSS rescore
  74. 2026-08-02 23:19 UTCEG score recompute
  75. 2026-08-02 02:27 UTCEPSS rescore

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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 on July 31, 2026, with the most recent update on September 8, 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 0.7% probability of exploitation in the next 30 days (52nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-53551?
CVE-2026-53551 has a CVSS base score of 6.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-53551?
A fix for CVE-2026-53551 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-53551 are linked in the Vendor Advisories panel on this page.

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