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VulnerabilityPublished Updated

CVE-2026-91766: PHP · Information Exposure

Affects PHPSource CVE Database V5

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Mentioned vulnerabilities

Not known to be exploited · CVSS 5.9 Medium · fixed in 8.5.11 : update PHP when convenient.

Data as of 8 Nov 2026, 23:24 UTC

CVSS 3.1 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 8.5.11, 8.4.26, 8.3.35 +1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 8 Nov 2026.

What to do

Upgrade PHP to 8.5.11, 8.4.26, 8.3.35 or 8.2.34.

Affected software

ProductAffectedFixed in
PHP GroupPHPAffected
  • ≥ 8.5.*, < 8.5.11
Fixed in
  • 8.5.11
PHP GroupPHPAffected
  • ≥ 8.4.*, < 8.4.26
Fixed in
  • 8.4.26
PHP GroupPHPAffected
  • ≥ 8.3.*, < 8.3.35
Fixed in
  • 8.3.35
PHP GroupPHPAffected
  • ≥ 8.2.*, < 8.2.34
Fixed in
  • 8.2.34

AI-suggested

If you cannot patch yet, avoid relying on redirects that could cause sensitive headers to be forwarded to unintended hosts or downgrade protocols.

Description

CVE-2026-91766 is a medium severity vulnerability in PHP where the http:// stream wrapper forwards sensitive headers such as Authorization, Cookie, and Proxy-Authorization unchanged when following redirects. This occurs even if the redirect target is a different host, port, or downgrades from HTTPS to HTTP, potentially exposing credentials to unintended servers.

References

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