CVE-2026-91768

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.6% (44th 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
Trending — 3 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

The IPv6 branch of the FastCGI client access check compares only the first 12 bytes of a 16-byte IPv6 address, so listen.allowed_clients matches on a /96 prefix instead of the exact address. An attacker who can source an address sharing the first 96 bits with an allowed one passes the check and reaches the FastCGI endpoint.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
29
EG Risk 29/100CISA 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
Severity65% × 45%
Exploitation1% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.6%
EPSS %ILE
44th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (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

September 25, 2026

Last Modified

September 29, 2026

Advisory Details (1)

Auto-updated Sep 25, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

IPv6 ACL bypass in FastCGI listen.allowed_clients due to partial address comparison (memcmp 12 bytes) · Advisory · php/php-src · GitHub

https://github.com/php/php-src/security/advisories/GHSA-62xp-839h-2637

Vendor Advisories for CVE-2026-91768(2)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatphp-main-8.5.11-2.hum12026-09-23redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 25× in last 7d / 31× 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. 2026-10-04 12:14 UTCEG score recompute
  2. 2026-10-04 12:14 UTCVendor advisory
  3. 2026-10-03 14:16 UTCEG score recompute
  4. 2026-10-03 14:16 UTCVendor advisory
  5. 2026-10-02 16:17 UTCVendor advisory
  6. 2026-10-02 16:17 UTCEG score recompute
  7. 2026-10-02 16:17 UTCVendor advisory
  8. 2026-10-01 19:51 UTCEPSS rescore
  9. 2026-10-01 18:18 UTCVendor advisory
  10. 2026-09-30 20:14 UTCEG score recompute
  11. 2026-09-30 20:14 UTCVendor advisory
  12. 2026-09-30 15:04 UTCEPSS rescore
  13. 2026-09-29 22:16 UTCEG score recompute
  14. 2026-09-29 22:16 UTCVendor advisory
  15. 2026-09-29 12:24 UTCEG score recompute
  16. 2026-09-29 12:24 UTCVendor advisory
  17. 2026-09-28 14:26 UTCEG score recompute
  18. 2026-09-28 14:26 UTCVendor advisory
  19. 2026-09-28 13:52 UTCEPSS rescore
  20. 2026-09-28 13:52 UTCEPSS rescore
  21. 2026-09-28 13:44 UTCEG score recompute
  22. 2026-09-28 13:44 UTCVendor advisory
  23. 2026-09-27 18:20 UTCEG score recompute
  24. 2026-09-27 18:20 UTCVendor advisory
  25. 2026-09-27 13:49 UTCEPSS rescore
Show 6 more
  1. 2026-09-26 20:21 UTCEG score recompute
  2. 2026-09-26 20:21 UTCVendor advisory
  3. 2026-09-26 15:59 UTCEPSS rescore
  4. 2026-09-25 22:22 UTCEG score recompute
  5. 2026-09-25 21:20 UTCEG score recompute
  6. 2026-09-25 21:19 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-91768?
CVE-2026-91768 is a medium vulnerability published on September 25, 2026. The IPv6 branch of the FastCGI client access check compares only the first 12 bytes of a 16-byte IPv6 address, so listen.allowed_clients matches on a /96 prefix instead of the exact address. An attacker who can source an address sharing the first 96 bits with an allowed one passes the check and…
When was CVE-2026-91768 disclosed?
CVE-2026-91768 was first published on September 25, 2026, with the most recent update on September 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-91768 actively exploited?
CVE-2026-91768 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (44th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-91768?
CVE-2026-91768 has a CVSS base score of 6.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-91768?
A fix for CVE-2026-91768 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-91768 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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