CVE-2026-73637 Apache HTTP Server: mod_auth_digest DoS attack

What is CVE-2026-73637?

CVE-2026-73637 is a high-severity use after free vulnerability in Apache Http Server, published on 1 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Use after free in mod_auth_digest in Apache Software Foundation Apache HTTP Server before 2.4.69 on all platforms allows an unauthenticated remote client to cause authentication state corruption via concurrent Digest authentication requests when AuthDigestNcCheck is enabled or AuthDigestNonceLifetime is set to 0.

Users are recommended to upgrade to version 2.4.69, which fixes this issue.

Weakness: CWE-416

Which versions are affected by CVE-2026-73637?

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

Products include Apache Http Server.

How do I fix CVE-2026-73637?

Upgrade apache to 2.4.69 or later.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-73637 being exploited?

There is no known exploitation of CVE-2026-73637 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-2026-73637, AZL-106785, BELL-CVE-2026-73637, BIT-apache-2026-73637, DEBIAN-CVE-2026-73637, ECHO-750c-31b0-1c4d and 4 more.