What’s Vulnerable › Vulnerabilities

CVE-2026-28780: Apache HTTP Server: buffer overflow in mod_proxy_ajp via ajp_msg_check_header()

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-05 · updated 2026-09-14
• Weakness: CWE-122

Description

Heap-based Buffer Overflow vulnerability in mod_proxy_ajp of Apache HTTP Server. If mod_proxy_ajp connects to a malicious AJP server this AJP server can send a malicious AJP message back to mod_proxy_ajp and cause it to write 4 attacker controlled bytes after the end of a heap based buffer. This issue affects Apache HTTP Server: through 2.4.66. Users are recommended to upgrade to version 2.4.67, which fixes the issue.

Affected products

• Apache HTTP Server: before 2.4.67 — fixed in 2.4.67

How to fix

Upgrade to a fixed version: Apache HTTP Server 2.4.67. Check the vendor advisory for mitigations.

References

• https://httpd.apache.org/security/vulnerabilities_24.html
• http://www.openwall.com/lists/oss-security/2026/05/05/9
• https://access.redhat.com/errata/RHSA-2026:21391
• https://access.redhat.com/errata/RHSA-2026:21433
• https://access.redhat.com/errata/RHSA-2026:22140
• https://access.redhat.com/errata/RHSA-2026:27200
• https://access.redhat.com/errata/RHSA-2026:27201
• https://access.redhat.com/errata/RHSA-2026:36373
• https://access.redhat.com/errata/RHSA-2026:36831
• https://access.redhat.com/errata/RHSA-2026:36846
• https://access.redhat.com/errata/RHSA-2026:47046
• https://access.redhat.com/errata/RHSA-2026:62165

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