CVE-2026-6104
CRITICAL severity · CVSS 9.1 · Out-of-bounds read
9.1CVSS CRITICAL
Summary
In PHP versions 8.4.* before 8.4.21 and 8.5.* before 8.5.6, when an encoding name containing an embedded NUL byte is passed to mb_convert_encoding() or related mbstring functions, the code incorrectly assumes that when strncasecmp() returns 0 it means the strings have the same length. This can lead to out-of-bounds read of global memory, potentially causing a crash or information disclosure or crash. Affected functions include mb_convert_encoding(), mb_detect_encoding(), mb_convert_variables(), and mb_detect_order(), as well as the mbstring.detect_order and mbstring.http_output INI settings.
Impact & exploitability
Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
Confidentiality impactHigh
Integrity impactNone
Availability impactHigh
Exploit probability (EPSS)0%
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Affected products we track (1)
Recommendation
Apply the vendor fix promptly. Open any affected product above for its exact safe version.
Additional information
- NVD record
- https://github.com/php/php-src/security/advisories/GHSA-74r9-qxhc-fx53Advisory
- https://access.redhat.com/errata/RHSA-2026:22649
- https://access.redhat.com/security/cve/CVE-2026-6104
- https://bugzilla.redhat.com/show_bug.cgi?id=2468573
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-6104.json