Apache HTTP Server 2.4.x AuthDigestNonceLifetime 0 Bypass via Capture-Replay MITM
CVE-2026-73636 Published on October 1, 2026
Apache HTTP Server: mod_auth_digest one-time-nonce replay attack
Authentication bypass by capture-replay in mod_auth_digest in Apache Software Foundation Apache HTTP Server 2.4.x on all platforms allows a man-in-the-middle (MITM) attacker to replay captured digest authentication credentials via crafted requests that trigger garbage collection of the client's shared memory entry when AuthDigestNonceLifetime is set to 0.
Users are recommended to upgrade to version 2.4.69, which fixes this issue.
Vulnerability Analysis
CVE-2026-73636 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Timeline
Report received
fixed in 2.4.x by r1937721 115 days later.
2.4.69 released
Weakness Type
Authentication Bypass by Capture-replay
A capture-replay flaw exists when the design of the software makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). Capture-replay attacks are common and can be difficult to defeat without cryptography. They are a subset of network injection attacks that rely on observing previously-sent valid commands, then changing them slightly if necessary and resending the same commands to the server.
Products Associated with CVE-2026-73636
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Affected Versions
Apache Software Foundation Apache HTTP Server:- Version 2.4.0, <= 2.4.68 is affected.