Apache HTTP Server: mod_ssl TLS upgrade attack
In some mod_ssl configurations on Apache HTTP Server versions through to 2.4.63, an HTTP desynchronisation attack allows a man-in-the-middle attacker to hijack an HTTP session via a TLS upgrade. Only configurations using "SSLEngine optional" to enable TLS upgrades are affected. Users are recommended to upgrade to version 2.4.64, which removes support for TLS upgrade.
02 / AFFECTED SOFTWARE
Affected packages
1 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In some mod_ssl configurations on Apache HTTP Server versions through to 2.4.63, an HTTP desynchronisation attack allows a man-in-the-middle attacker to hijack an HTTP session via a TLS upgrade. Only configurations using "SSLEngine optional" to enable TLS upgrades are affected. Users are recommended to upgrade to version 2.4.64, which removes support for TLS upgrade.
In some mod_ssl configurations on Apache HTTP Server versions through to 2.4.63, an HTTP desynchronisation attack allows a man-in-the-middle attacker to hijack an HTTP session via a TLS upgrade. Only configurations using "SSLEngine optional" to enable TLS upgrades are affected. Users are recommended to upgrade to version 2.4.64, which removes support for TLS upgrade.
05 / REFERENCES
Further evidence
- http://www.openwall.com/lists/oss-security/2025/07/09/3
- http://www.openwall.com/lists/oss-security/2025/07/10/2
- http://www.openwall.com/lists/oss-security/2025/07/10/9
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/49xxx/CVE-2025-49812.json
- https://httpd.apache.org/security/vulnerabilities_24.html
- https://lists.debian.org/debian-lts-announce/2025/08/msg00009.html
- https://nvd.nist.gov/vuln/detail/CVE-2025-49812