CVE-2026-91766

MEDIUMNVD 5.95.9
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This medium-severity CVE scores 5.9 under NVD CVSS v3. EPSS exploit probability: 0.3% (21st percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3

Also known asEUVD-2026-87357 (ENISA EUVD)Source: ENISA EUVD

5.9EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • 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 27/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity59% × 45%
Impact severity (EG Severity): CVSS 5.9 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
21st
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.9): severity, escalated by confirmed exploitation. This CVE's 5.9 is its impact severity (EG Severity), not escalated.

EG Severity
5.9 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track 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). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

September 25, 2026

Last Modified

October 23, 2026

Advisory Details (1)

Auto-updated Sep 25, 2026
Patch available. Sources: github.
GitHub advisoryMentions a patch (unverified)

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(3)

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

Patch Availability(3)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntuphp8.3-zip (8.3.6-0ubuntu0.24.04.12) @ noble2026-10-23ubuntu
redhatphp:7.4-8100020261021081045.f79986652026-10-21redhat
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.

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
php8.28.2.10-1 ... 8.2.7-1~deb12u1 (29 versions)
  • every version up to 8.2.34-1~deb12u1: fixed in 8.2.34-1~deb12u1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
php8.48.4.11-1 ... 8.4.24-1~deb13u1 (11 versions)
  • every version up to 8.4.26-1~deb13u1: fixed in 8.4.26-1~deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
php8.48.4.11-1 ... 8.4.26-1~deb13u1 (12 versions)
  • every version up to 8.4.26-1: fixed in 8.4.26-1
—

Weakness Classification(2)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 7× in last 7d / 55× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 81 is merged into the row it repeats.

  1. 2026-11-01 16:36 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  2. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  3. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  4. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  5. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  6. 2026-10-27 16:33 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  7. 2026-10-26 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  8. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  9. 2026-10-25 13:51 UTCEG score recompute
  10. 2026-10-24 16:34 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  11. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  12. 2026-10-23 14:07 UTCEG score recompute
  13. 2026-10-23 14:07 UTCVendor advisory
  14. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  15. 2026-10-22 12:30 UTCEG score recompute
  16. 2026-10-22 12:30 UTCVendor advisory
  17. 2026-10-21 16:34 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  18. 2026-10-20 16:34 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  19. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  20. 2026-10-18 16:33 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  21. 2026-10-18 03:00 UTCEG score recompute
  22. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  23. 2026-10-16 16:45 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  24. 2026-10-15 16:33 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  25. 2026-10-14 16:34 UTCEPSS rescoreEPSS 0.3% · 25th percentile
Show 55 more
  1. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  2. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  3. 2026-10-12 14:45 UTCEG score recompute
  4. 2026-10-11 19:13 UTCEG score recompute
  5. 2026-10-11 16:30 UTCEG score recompute
  6. 2026-10-11 15:24 UTCEG score recompute
  7. 2026-10-11 15:24 UTCVendor advisory
  8. 2026-10-11 13:50 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  9. 2026-10-11 13:44 UTCEG score recompute
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  11. 2026-10-10 13:54 UTCEG score recompute
  12. 2026-10-10 13:54 UTCVendor advisory
  13. 2026-10-09 20:08 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  14. 2026-10-09 12:21 UTCEG score recompute
  15. 2026-10-09 12:21 UTCVendor advisory
  16. 2026-10-08 17:14 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  17. 2026-10-08 10:49 UTCEG score recompute
  18. 2026-10-08 10:49 UTCVendor advisory
  19. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  20. 2026-10-07 09:19 UTCEG score recompute
  21. 2026-10-07 09:19 UTCVendor advisory
  22. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  23. 2026-10-06 07:45 UTCEG score recompute
  24. 2026-10-06 07:45 UTCVendor advisory
  25. 2026-10-05 17:44 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  26. 2026-10-05 06:16 UTCEG score recompute
  27. 2026-10-05 06:16 UTCVendor advisory
  28. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  29. 2026-10-04 04:46 UTCEG score recompute
  30. 2026-10-04 04:46 UTCVendor advisory
  31. 2026-10-03 03:17 UTCEG score recompute
  32. 2026-10-03 03:17 UTCVendor advisory
  33. 2026-10-02 01:47 UTCEG score recompute
  34. 2026-10-02 01:47 UTCVendor advisory
  35. 2026-10-01 19:51 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  36. 2026-10-01 00:15 UTCEG score recompute
  37. 2026-10-01 00:15 UTCVendor advisory
  38. 2026-09-30 15:04 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  39. 2026-09-29 22:16 UTCVendor advisory
  40. 2026-09-29 15:55 UTCEG score recompute
  41. 2026-09-29 15:55 UTCVendor advisory
  42. 2026-09-28 14:26 UTCEG score recompute
  43. 2026-09-28 14:26 UTCVendor advisory
  44. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  45. 2026-09-28 13:44 UTCEG score recompute
  46. 2026-09-28 13:44 UTCVendor advisory
  47. 2026-09-28 00:18 UTCEG score recompute
  48. 2026-09-28 00:18 UTCVendor advisory
  49. 2026-09-27 13:49 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  50. 2026-09-26 22:48 UTCEG score recompute
  51. 2026-09-26 22:48 UTCVendor advisory
  52. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  53. 2026-09-25 21:19 UTCEG score recompute
  54. 2026-09-25 20:46 UTCEG score recomputeFirst assessed: 5.9 MEDIUM
  55. 2026-09-25 20:44 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-91766?
CVE-2026-91766 is a medium-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-91766 published?
The CVE record for CVE-2026-91766 was published on September 25, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 23, 2026; the record at its source may have been updated since.
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 (21st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-91766?
CVE-2026-91766 has a CVSS v3 base score of 5.9 (NVD).
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

See which npm, PyPI, Go, and Maven packages are affected by 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