CVE-2026-57941: Use-After-Free Vulnerability in Apache HTTP Server mod_http2
A memory-safety vulnerability identified as CVE-2026-57941 affects Apache HTTP Server's mod_http2 module. The issue involves a use-after-free condition associated with a shared session buffer and re-entrant processing.
The Apache HTTP Server project's advisory lists versions from 2.4.17 through 2.4.68 as affected and identifies Apache HTTP Server 2.4.69 as the release containing the fix. The issue was publicly disclosed on October 1, 2026.
Administrators managing internet-facing web servers should review their installed versions, confirm whether the affected module is enabled, and follow the security guidance provided by Apache and their operating system vendor.
What Is CVE-2026-57941?
CVE-2026-57941 is a use-after-free vulnerability in Apache HTTP Server's HTTP/2 implementation, specifically the mod_http2 module.
A use-after-free occurs when a program continues to access memory after that memory has been released. Depending on how the affected code executes, this type of bug can cause unexpected behavior, process crashes, or memory corruption.
The published description identifies re-entrant processing involving the shared session->bbtmp buffer as part of the problem. Re-entrancy can become dangerous when a function is called again before an earlier operation has fully completed and shared state is not handled safely.
The vulnerability is related to internal memory management. It does not mean that every Apache HTTP Server installation is automatically exploitable, and the existence of a use-after-free flaw alone does not prove that arbitrary code execution is possible.
Which Versions Are Affected?
According to the Apache HTTP Server project's security advisory:
Product: Apache HTTP Server
Affected component: mod_http2
Affected versions: 2.4.17 through 2.4.68, as listed by Apache
Vulnerability class: Use-after-free / memory corruption
CWE: CWE-416
Fixed upstream release: Apache HTTP Server 2.4.69
Fix release date: October 1, 2026
Version ranges can differ between upstream records and the package metadata maintained by operating system vendors. Administrators should therefore check the advisory for their particular distribution instead of relying exclusively on a generic version comparison.
Apache classifies the issue as moderate in its project advisory. Severity ratings shown by other vulnerability databases may differ, so the vendor's description and the deployment's actual exposure should both be considered.
Why Is This Relevant to Web Server Administrators?
Apache HTTP Server is commonly used to serve websites, applications, APIs, and other web-facing services.
A memory-safety issue inside an enabled protocol module deserves attention because unexpected memory access can affect server stability and may create security risks, depending on the execution path and surrounding protections.
Potential concerns include:
Unexpected worker-process failures or service instability.
Memory corruption in a process handling HTTP/2 traffic.
Additional security exposure if the bug can be reached through a deployed configuration.
Wider operational consequences for applications relying on the affected web server.
These are potential consequences of the vulnerability class, not a claim that each outcome has been demonstrated for every configuration affected by CVE-2026-57941.
Recommended Mitigation
1. Upgrade to a Fixed Version
Apache HTTP Server 2.4.69 includes the upstream fix for this vulnerability.
Administrators should upgrade to 2.4.69 or a later supported release containing the correction. If Apache is provided through a Linux distribution, container image, managed hosting service, or commercial platform, check the corresponding vendor advisory for the fixed package.
Do not assume a package is vulnerable or fixed solely by comparing its displayed version string. Some vendors backport security fixes without changing the upstream version number in the same way.
2. Check Whether HTTP/2 Is Enabled
Review the server's loaded modules and configuration to determine whether mod_http2 is in use.
The risk assessment should consider whether the affected code path is reachable in the deployed environment. Disabling an unused component can reduce exposure, but it should not be treated as a substitute for installing the supported security update.
3. Apply Temporary Mitigation if Updating Is Delayed
Red Hat's advisory recommends disabling mod_http2 until a fixed package is installed as a temporary mitigation for affected environments.
Before changing production configuration, consult your distribution's instructions, evaluate the impact on HTTP/2 traffic, and test the change. Restart the server as required and verify that the service remains available.
Temporary configuration changes should be removed or reassessed once the fixed package has been deployed.
4. Verify the Deployment After Updating
After remediation, confirm the installed package version, check the module configuration, validate service startup, and review logs for unexpected failures.
Where the server supports centralized inventory or vulnerability scanning, record the resolved status so affected hosts are not overlooked during later maintenance.
Conclusion
CVE-2026-57941 is a use-after-free vulnerability in Apache HTTP Server's mod_http2 module involving shared session-buffer handling.
The Apache project's advisory identifies versions through 2.4.68 as affected and Apache HTTP Server 2.4.69 as containing the fix. Administrators should prioritize inventory and remediation of affected deployments, using official upstream and distribution-specific guidance.
Keeping internet-facing server software patched remains an important part of protecting service availability and reducing exposure to memory-safety defects.
References
Information checked on October 13, 2026. Check the current Apache and distribution advisories before making production changes.
