Improper input validation in MySQL Server - CVE-2026-34303

Vulnerability identifier: #VU126774

CSH Severity: Medium

CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-34303

CWE-ID: CWE-125

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote authenticated user to perform a denial of service (DoS) attack.

The vulnerability exists due to improper input validation within the Server: Optimizer component in MySQL Server. A remote authenticated user can exploit this vulnerability to perform a denial of service (DoS) attack.

MySQL Server
Anolis OS
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
openEuler
Ubuntu
Fedora
mecab
mecab-ipadic-EUCJP
mecab-ipadic
mysql-8.0 (Ubuntu package)
mysql-debuginfo
mysql-config
mysql-common
mysql
mysql-test
mysql-server
mysql-libs
mysql-help
mysql-errmsg
mysql-devel
mysql-debugsource
mysql (Red Hat package)
mysql8.4 (Red Hat package)
mysql8.4

Install updates from vendor's website.

mecab - update to 0.996-2
mecab-ipadic-EUCJP - update to 2.7.0.20070801-17.0.1
mecab-ipadic - update to 2.7.0.20070801-17.0.1
mysql-8.0 (Ubuntu package) - addressed in versions 8.0.46-0ubuntu0.20.04.1+esm2, 8.0.46-0ubuntu0.22.04.2, 8.0.46-0ubuntu0.24.04.2, 8.4.9-0ubuntu0.25.10.1, 8.4.9-0ubuntu0.26.04.1
mysql-debuginfo - update to 8.0.46-1
mysql-config - update to 8.0.46-1
mysql-common - update to 8.0.46-1
mysql - update to 8.0.46-1
mysql-test - update to 8.0.46-1
mysql-server - update to 8.0.46-1
mysql-libs - update to 8.0.46-1
mysql-help - update to 8.0.46-1
mysql-errmsg - update to 8.0.46-1
mysql-devel - update to 8.0.46-1
mysql-debugsource - update to 8.0.46-1
mysql - addressed in versions 8.0.46-1, 8.0.46-1.0.1
mysql-common - addressed in versions 8.0.46-1, 8.0.46-1.0.1
mysql-devel - addressed in versions 8.0.46-1, 8.0.46-1.0.1
mysql-errmsg - addressed in versions 8.0.46-1, 8.0.46-1.0.1
mysql-libs - addressed in versions 8.0.46-1, 8.0.46-1.0.1
mysql-server - addressed in versions 8.0.46-1, 8.0.46-1.0.1
mysql-test - addressed in versions 8.0.46-1, 8.0.46-1.0.1
mysql (Red Hat package) - update to 8.0.46-1.el9_8
mysql8.4 (Red Hat package) - update to 8.4.9-1.el10_2
mysql8.4 - addressed in versions 8.4.9-1.fc42, 8.4.9-1.fc43, 8.4.9-1.fc44

• https://www.oracle.com/security-alerts/cpuapr2026.html

• Multiple vulnerabilities in MySQL Server
• openEuler 24.03 LTS SP1 update for mysql
• openEuler 24.03 LTS update for mysql
• openEuler 24.03 LTS SP3 update for mysql
• openEuler 22.03 LTS SP4 update for mysql
• openEuler 20.03 LTS SP4 update for mysql
• Fedora 43 update for mysql8.4
• Fedora 44 update for mysql8.4
• Fedora 42 update for mysql8.4
• Red Hat Enterprise Linux 10 update for mysql8.4
• Anolis OS update for mysql
• Ubuntu update for mysql-8.0
• Ubuntu update for mysql-8.0
• Red Hat Enterprise Linux 9 update for mysql
• Red Hat Enterprise Linux 8 update for the mysql:8.0 module
• Red Hat Enterprise Linux 8 update for the mysql:8.4 module
• Anolis OS update for mysql:8.0 module