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Vulnerability record · CVE-2026-6104 · published 10 May 2026

CVE-2026-6104: Php out-of-bounds read vulnerability

Php · Php

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.

6.3 CVSS 4.0 Medium EPSS 0.60% · top 53.3% CWE-125 · Out-of-bounds read
6.3CVSS 4.0 base score
0.60%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
5References
24 Jul 2026Last modified by NVD

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.

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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
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

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-6104), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.