CVE-2026-6104
CRITICAL9.1EPSS 0.02%Global buffer over-read in mb_convert_encoding() with attacker-supplied encoding
Published: 5/10/2026Modified: 5/15/2026
Description
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.
Affected packages (4)
- Bitnami/libphp>= 8.4.0, < 8.4.21, >= 8.5.0, < 8.5.6
- Bitnami/php>= 8.4.0, < 8.4.21, >= 8.5.0, < 8.5.6
- Bitnami/php-min>= 8.4.0, < 8.4.21, >= 8.5.0, < 8.5.6
- Debian/php8.4from 0, < 8.4.21-1~deb13u1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:L/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:M/U:Amber |
| osv | CVSS 3.1 | CRITICAL9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H |