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Fencer Vulns
high 8.2

CVE-2026-6104 json

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

published 2026-05-07 6 mo ago modified 2026-09-10 59 d ago also BIT-libphp-2026-6104 , BIT-php-2026-6104 , BIT-php-min-2026-6104 , EUVD-2026-28979 , GHSA-74r9-qxhc-fx53

cvss
8.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

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.

Patch / fix

  • bitnami libphp 8.4.21, 8.5.6
  • bitnami php 8.4.21, 8.5.6
  • bitnami php-min 8.4.21, 8.5.6
  • PHP Group PHP 8.4.21, 8.5.6
  • Red Hat Red Hat Enterprise Linux 10 0:8.4.21-1.el10_2
  • php8.4 Debian 13 8.4.21-1~deb13u1
  • php8.4 Debian 14 8.4.21-1

debian advisories DEBIAN-CVE-2026-6104

  • php8.4 Ubuntu 25.10 8.4.11-1ubuntu1.2
  • php8.5 Ubuntu 26.04 LTS 8.5.4-0ubuntu1.1

ubuntu advisories UBUNTU-CVE-2026-6104

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • php8.4 RHEL 10.2 8.4.21-1.el10_2
  • php8.4-gd RHEL 10.2 8.4.21-1.el10_2
  • php8.4-cli RHEL 10.2 8.4.21-1.el10_2
  • php8.4-dba RHEL 10.2 8.4.21-1.el10_2
  • php8.4-dbg RHEL 10.2 8.4.21-1.el10_2
  • php8.4-ffi RHEL 10.2 8.4.21-1.el10_2
  • php8.4-fpm RHEL 10.2 8.4.21-1.el10_2
  • php8.4-gmp RHEL 10.2 8.4.21-1.el10_2

red hat advisories RHSA-2026:22649

  • php8 openSUSE Tumbleweed 8.5.6-1.1

opensuse advisories openSUSE-SU-2026:10747-1

  • php8.4 AlmaLinux 10 8.4.21-1.el10_2
  • php8.4-gd AlmaLinux 10 8.4.21-1.el10_2
  • php8.4-cli AlmaLinux 10 8.4.21-1.el10_2
  • php8.4-dba AlmaLinux 10 8.4.21-1.el10_2
  • php8.4-dbg AlmaLinux 10 8.4.21-1.el10_2
  • php8.4-ffi AlmaLinux 10 8.4.21-1.el10_2
  • php8.4-fpm AlmaLinux 10 8.4.21-1.el10_2
  • php8.4-gmp AlmaLinux 10 8.4.21-1.el10_2

almalinux advisories ALSA-2026:22649

  • php8.4 Rocky Linux 10 8.4.21-1.el10_2

rocky linux advisories RLSA-2026:22649

  • php84 Alpine 3.22 8.4.27-r0
  • php84 Alpine 3.23 8.4.21-r0
  • php85 Alpine 3.24, Alpine 3.23 8.5.6-r0

alpine advisories ALPINE-CVE-2026-6104

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-6104 updated cvss 8.2

php: global buffer over-read in mb_convert_encoding() with attacker-supplied encoding

  • Red Hat Enterprise Linux AppStream (v. 10) php8.4 8.4.21-1.el10_2, php8.4-gd 8.4.21-1.el10_2, php8.4-cli 8.4.21-1.el10_2, php8.4-dba 8.4.21-1.el10_2, php8.4-dbg 8.4.21-1.el10_2, php8.4-ffi 8.4.21-1.el10_2, +18 more
    fixed: vendor fix RHSA-2026:22649
  • Red Hat Enterprise Linux 6 php, php-gd, php-cli, php-dba, php-fpm, php-pdo, +20 more Red Hat Enterprise Linux 7 php, php-gd, php-cli, php-dba, php-fpm, php-pdo, +18 more Red Hat Enterprise Linux 8 php, libzip, php-gd, php-cli, php-dba, php-dbg, +30 more Red Hat Enterprise Linux 9 php, php-gd, php-cli, php-dba, php-dbg, php-ffi, +18 more Red Hat Enterprise Linux 10 php Red Hat Hardened Images php
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
5 mo ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 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
CISA ADP 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
CNA 4.0 6.3 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
NVD 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
CNA 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
OSV 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami libphp
>=8.4.0, <8.4.21
>=8.5.0, <8.5.6
8.4.21
8.5.6
bitnami php
>=8.4.0, <8.4.21
>=8.5.0, <8.5.6
8.4.21
8.5.6
bitnami php-min
>=8.4.0, <8.4.21
>=8.5.0, <8.5.6
8.4.21
8.5.6

Affected products

  • PHP Group PHP
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Hardened Images

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of php/php-src published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.