Apache HTTP Server mod_http2 double-free remote code execution
Apache HTTP Server versions prior to 2.4.67 contain a critical double-free vulnerability in mod_http2 enabling remote code execution on certain configurations.
Sourcecisecurity.org — open the original
What to check
- Applies to
- The 1 CVE named below. Whether you run an affected version is not assessed: check the versions the source lists.
- Exploitation
- A public exploit is recorded for CVE-2026-23918 (poc); no exploitation in the wild is recorded.
A critical vulnerability (CVE-2026-23918) has been discovered in Apache HTTP Server's mod_http2 module affecting versions prior to 2.4.67. The flaw is a double-free memory corruption issue triggered by crafted HTTP/2 sequences that cause the same stream to be cleaned up twice. Attackers can exploit this vulnerability with minimal effort to crash worker processes, achieving denial of service. More critically, on systems using APR with mmap—common configurations on Debian systems and official Docker images—the vulnerability can be leveraged to achieve remote code execution.
Proof of concept code is publicly available for both denial of service and code execution attacks, significantly lowering the barrier to exploitation. The vulnerability requires no authentication and can be exploited remotely through public-facing Apache HTTP Server instances running the affected versions. Organizations running Apache HTTP Server should prioritize immediate patching to version 2.4.67 or later.
The MS-ISAC advisory categorizes this as a high-risk threat across government, business, and home user environments. Given the widespread deployment of Apache HTTP Server and the availability of exploit code, this vulnerability represents a significant attack surface for initial access operations targeting internet-facing web infrastructure.
Mentioned in this report
Source reporting: https://www.cisecurity.org/advisory/a-vulnerability-in-apache-http-server-could-allow-for-remote-code-execution_2026-044
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