CVE-2026-43951 Apache HTTP Server: OOB Read in `merge_response_headers` can cause crash

What is CVE-2026-43951?

CVE-2026-43951 is a medium-severity memory corruption vulnerability in Apache Http Server, published on 8 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Out-of-bounds Read vulnerability in Apache HTTP Server with mod_headers and mod_mime and multiple response languages.

This issue affects Apache HTTP Server: from 2.4.0 through 2.4.67.

Weakness: CWE-125

Which versions are affected by CVE-2026-43951?

1 open source package ship an affected version, including apache. It affects 1 product.

Products include Apache Http Server.

How do I fix CVE-2026-43951?

Upgrade apache to 2.4.68 or later.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-43951 being exploited?

There is no known exploitation of CVE-2026-43951 in the wild and no public exploit code.

Other vulnerabilities in Apache Http Server

• CVE-2021-42013 Apache HTTP Server Path Traversal Exploited Critical 9.8
• CVE-2024-38475 Apache HTTP Server Improper Escaping of Output Exploited Critical 9.1
• CVE-2021-40438 Apache HTTP Server-Side Request Forgery (SSRF) Exploited Critical 9.0
• CVE-2019-0211 Apache HTTP Server Privilege Escalation Exploited High 7.8
• CVE-2021-41773 Apache HTTP Server Path Traversal Exploited High 7.5

All Apache Http Server vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2026-43951, AZL-89712, AZL-89729, BELL-CVE-2026-43951, BIT-apache-2026-43951, CLSA-2026-1782209860 and 7 more.