CVE-2026-91769
Description
A flaw was found in PHP. This vulnerability allows server impersonation and potential information disclosure during Transport Layer Security (TLS) connections. When verifying peer certificates, PHP improperly falls back to matching the Common Name (CN) if no Subject Alternative Name (SAN) matches the requested hostname. An attacker could exploit this flaw by presenting a certificate trusted for another domain whose CN matches the target, enabling them to impersonate a legitimate server and intercept sensitive data.
Statement
This vulnerability is evaluated as Moderate impact because an attacker must achieve an active man-in-the-middle network position and present a trusted certificate possessing a matching Common Name alongside disparate Subject Alternative Names. Exposure in Red Hat environments is restricted to outbound TLS client connections established via PHP streams; inbound application traffic processed by PHP-FPM or mod_php is unaffected. Furthermore, public certificate authorities generally disallow conflicting identity combinations, limiting the real-world attack surface.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.3 | N/A | 4.3 |
| Attack Vector | Adjacent Network | N/A | Adjacent Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
cve.org: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Understanding the Weakness (CWE)
Integrity,Authentication
Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity
When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The product might connect to a malicious host while believing it is a trusted host, or the product might be deceived into accepting spoofed data that appears to originate from a trusted host.
Frequently Asked Questions
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