CVE-2026-91766

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (24th 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
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

When the http:// stream wrapper follows a redirect it forwards the user-supplied Authorization, Cookie and Proxy-Authorization headers unchanged, even when the redirect target is a different host, a different port, or a downgrade from HTTPS to HTTP. A server that can steer a redirect therefore receives credentials that were only meant for the original origin. This is the same class of issue that libcurl fixed in 7.58.0 ( CVE-2018-1000007 https://github.com/advisories/GHSA-g7x2-hrfp-pv5f ).

CVSS v3
5.9
EG Score
5.9MEDIUMmedium confidence
EG Risk
27
EG Risk 27/100CISA 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
Severity59% × 45%
Exploitation0% × 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
0.3%
EPSS %ILE
24th
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

Cross-origin credential leak in HTTP stream wrapper redirects · Advisory · php/php-src · GitHub

Affected: 7.58.0 (

https://github.com/php/php-src/security/advisories/GHSA-fpwc-w8rq-cr92

Vendor Advisories for CVE-2026-91766(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(2)

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

Data Freshness Timeline

(refreshed 22× in last 7d / 28× 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 04:46 UTCEG score recompute
  2. 2026-10-04 04:46 UTCVendor advisory
  3. 2026-10-03 03:17 UTCEG score recompute
  4. 2026-10-03 03:17 UTCVendor advisory
  5. 2026-10-02 01:47 UTCEG score recompute
  6. 2026-10-02 01:47 UTCVendor advisory
  7. 2026-10-01 19:51 UTCEPSS rescore
  8. 2026-10-01 00:15 UTCEG score recompute
  9. 2026-10-01 00:15 UTCVendor advisory
  10. 2026-09-30 15:04 UTCEPSS rescore
  11. 2026-09-29 22:16 UTCVendor advisory
  12. 2026-09-29 15:55 UTCEG score recompute
  13. 2026-09-29 15:55 UTCVendor advisory
  14. 2026-09-28 14:26 UTCEG score recompute
  15. 2026-09-28 14:26 UTCVendor advisory
  16. 2026-09-28 13:52 UTCEPSS rescore
  17. 2026-09-28 13:52 UTCEPSS rescore
  18. 2026-09-28 13:44 UTCEG score recompute
  19. 2026-09-28 13:44 UTCVendor advisory
  20. 2026-09-28 00:18 UTCEG score recompute
  21. 2026-09-28 00:18 UTCVendor advisory
  22. 2026-09-27 13:49 UTCEPSS rescore
  23. 2026-09-26 22:48 UTCEG score recompute
  24. 2026-09-26 22:48 UTCVendor advisory
  25. 2026-09-26 15:59 UTCEPSS rescore
Show 3 more
  1. 2026-09-25 21:19 UTCEG score recompute
  2. 2026-09-25 20:46 UTCEG score recompute
  3. 2026-09-25 20:44 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-91766?
CVE-2026-91766 is a medium vulnerability published on September 25, 2026. When the http:// stream wrapper follows a redirect it forwards the user-supplied Authorization, Cookie and Proxy-Authorization headers unchanged, even when the redirect target is a different host, a different port, or a downgrade from HTTPS to HTTP. A server that can steer a redirect therefore…
When was CVE-2026-91766 disclosed?
CVE-2026-91766 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-2026-91766 actively exploited?
CVE-2026-91766 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (24th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-91766?
CVE-2026-91766 has a CVSS base score of 5.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-91766?
A fix for CVE-2026-91766 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-91766 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-91766

Explore →

Is Your Infrastructure Affected by CVE-2026-91766?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Book a Demo →Browse All CVEs