CVE-2026-28780

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.

What this means for your business

It affects Apache Http Server. It matters if your company, or a supplier that handles your data, runs it.
An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
FIRST's prediction model gives it a 1% chance of attack attempts being seen in the next 30 days, ranking above 70% of all known flaws.

What to do

1Check whether your company or your suppliers run Apache Http Server, and which version. The affected versions are listed further down this page.
2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

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Scoring

CVSS: 9.8 (v3.1)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-122
Assigned by: security@apache.org

Dates

Published: 2026-05-05
Last modified: 2026-09-14
Sources: NVD

Affected products

Apache Http Server- 2.4.67

As listed in the NVD configuration data. Not a statement about your estate.