What is CVE-2026-6104?

CVE-2026-6104 is a critical-severity vulnerability in Php, classified under Out-of-bounds Read. CVSS score: 9.1/10. Published 2026-05-10.

How severe is CVE-2026-6104?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Out-of-bounds Read in Php

CVE-2026-6104

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() return…

Vulnerability class: Buffer Overflow

EPSS: 0.000 (10.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H.

Affected products

Php
Php Group — versions 8.4.*, 8.5.*

Weakness classification (CWE)

CWE-125 — Out-of-bounds Read

References

security@php.net (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-6104?: CVE-2026-6104 is a critical-severity vulnerability in Php, classified under Out-of-bounds Read. CVSS score: 9.1/10. Published 2026-05-10.
How severe is CVE-2026-6104?: Critical severity. CVSS v3 base score is 9.1 out of 10.