CVE-2026-91766Public exploitNetwork attack vectorHinoki check available

Credential disclosure via cross-origin redirect header forwarding

Published Sep 25, 2026 · Updated Sep 25, 2026

Credential exposure in affected PHP releases allows remote attackers to steal credentials through cross-origin HTTP redirects. The HTTP stream wrapper reuses user-supplied Authorization, Cookie, and Proxy-Authorization headers after a redirect changes the request origin. An application must send those headers through an HTTP stream with redirect following enabled, after which a redirecting server receives the caller's bearer token, session cookie, or proxy credentials.

CVSS severity5.9
Medium
EPSS probability0.34%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Credential exposure in affected PHP releases allows remote attackers to steal credentials through cross-origin HTTP redirects. The HTTP stream wrapper reuses user-supplied Authorization, Cookie, and Proxy-Authorization headers after a redirect changes the request origin. An application must send those headers through an HTTP stream with redirect following enabled, after which a redirecting server receives the caller's bearer token, session cookie, or proxy credentials.

The record

CVE
CVE-2026-91766
Published
Sep 25, 2026
Updated
Sep 25, 2026
Vendor
PHP Development Team
Product
PHP
Classifications
CWE-522, CWE-200, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=8.2.* <8.2.34
  2. Affected versionversion=8.3.* <8.3.35
  3. Affected versionversion=8.4.* <8.4.26
  4. Affected versionversion=8.5.* <8.5.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PHP Development Team · PHPversion=8.2.* <8.2.34; version=8.3.* <8.3.35; version=8.4.* <8.4.26; version=8.5.* <8.5.11

Published CVSS scores

5.9GitHub Security AdvisoryCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-522Insufficiently Protected Credentials
CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1539Steal Web Session Cookie

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

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