CVE-2025-49812

An HTTP session hijacking flaw was found in Apache httpd. In some mod_ssl configurations on Apache HTTP Server, an HTTP desynchronization attack allows a man-in-the-middle attacker to hijack an HTTP session via a TLS upgrade.

Only configurations using the "SSLEngine optional" to enable TLS upgrades are affected.

This vulnerability is rated Moderate rather than Important primarily due to the narrow scope of affected configurations and preconditions required for exploitation. Specifically, it only impacts Apache HTTP Server setups where SSLEngine optional is used—a rarely employed configuration that permits opportunistic TLS upgrades (also known as STARTTLS-style negotiation). For an attacker to successfully exploit this flaw, a man-in-the-middle (MitM) position is required, and the server must be using this optional TLS upgrade setup, which is uncommon and discouraged in modern secure deployments. The vulnerability arises due to HTTP desynchronization, allowing the attacker to potentially hijack sessions during the upgrade process.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.