Medium 6.3Published May 10, 2026

CVE-2026-6104Global buffer over-read in mb_convert_encoding() with attacker-supplied encoding

Updated under an hour ago (Oct 27, 2026, 9:00 PM ET)

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It affects PHP Group PHP and 3 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 6.3 MEDIUM (v4.0, CNA)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/RE:M/U:Amber
Weakness (CWE): CWE-125
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: php
NVD analysis: Modified
Record last updated: Jul 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

PHP Group PHP php_group:php (from the name)	from 8.4.* before 8.4.21; from 8.5.* before 8.5.6	CNA record
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux	from 0:8.4.21-1.el10_2 not affected	CISA ADP
Red Hat Red Hat Hardened Images redhat:hummingbird	1	CISA ADP
php php php:php	from 8.4.0 before 8.4.21; from 8.5.0 before 8.5.6	NVD

References

References

https://github.com/php/php-src/security/advisories/GHSA-74r9-qxhc-fx53	vendor-advisory
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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.