CVE-2025-49812
Description
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.
Statement
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.
Mitigation
No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.4 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | High | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Integrity,Non-Repudiation,Access Control
Technical Impact: Unexpected State; Hide Activities; Bypass Protection Mechanism
An attacker could create HTTP messages to exploit a number of weaknesses including 1) the message can trick the web server to associate a URL with another URL's webpage and caching the contents of the webpage (web cache poisoning attack), 2) the message can be structured to bypass the firewall protection mechanisms and gain unauthorized access to a web application, and 3) the message can invoke a script or a page that returns client credentials (similar to a Cross Site Scripting attack).
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