Apache has released Apache HTTP Server version 2.4.67 to address five security vulnerabilities, including a critical flaw that may allow remote code execution over HTTP/2 (CVE-2026-23918). Read this Cybersecurity Threat Advisory now to mitigate you and your clients’ risk.
What is the threat?
The most severe vulnerability, CVE-2026-23918 which has a CVSS score of 8.8, affects HTTP/2 handling in Apache 2.4.66. Under certain reset conditions, specially crafted HTTP/2 requests can allow an attacker to execute code with the same privileges as the web server—or crash the service. This issue only applies when HTTP/2 is enabled.
Additional vulnerabilities include:
- CVE-2026-24072 (Moderate) – A mod_rewrite issue allowing users with
.htaccessaccess to read unintended files, potentially exposing sensitive data. - CVE-2026-28780 (Low) – A mod_proxy_ajp flaw that could be exploited by a compromised AJP backend to manipulate message handling.
- CVE-2026-29168 (Low) – A mod_md issue where oversized OCSP responses can consume excessive resources and impact performance.
- CVE-2026-29169 (Low) – A mod_dav_lock flaw that can trigger server crashes via crafted requests (denial of service).
Collectively, these issues can enable code execution, unauthorized access, or service disruption on Apache versions up to 2.4.66 (with mod_md affected from 2.4.30 onward).
Why is it noteworthy?
Apache HTTP Server remains one of the most widely used web servers, making vulnerabilities in core features like HTTP/2 particularly impactful. Because HTTP/2 is common in modern deployments, attackers are likely to rapidly develop exploits and scan for exposed systems.
The presence of additional flaws in widely used modules (rewrite rules, AJP connections, certificate handling) further broadens the attack surface. Even without full remote code execution, these vulnerabilities can still lead to data exposure, instability, or service disruption.
For many organizations, this translates to potential downtime, loss of customer trust, or a pathway for attackers to move deeper into internal networks—making prompt patching essential.
What is the exposure or risk?
Organizations running Apache 2.4.66 with HTTP/2 enabled face the highest risk, including potential remote compromise. Attackers may execute commands, deploy malware or web shells, and use the server to pivot into internal systems—leading to data theft or broader compromise.
Additional risks include:
- Privilege abuse in shared environments: Users with
.htaccessaccess may read sensitive files, including credentials. - Service instability: Systems using AJP, OCSP, or WebDAV features may experience crashes or degraded performance.
- Denial of service: Attackers may disrupt availability even without full system compromise.
Delaying patching increases exposure, particularly for Internet-facing systems, as exploit activity is likely to grow quickly.
What are the recommendations?
Barracuda strongly recommends organizations take the following actions to reduce risk:
- Update all Apache servers to version 2.4.67, prioritizing Internet-facing and critical systems.
- Temporarily disable HTTP/2 on affected servers.
- Remove mod_dav_lock if not required to reduce DoS risk.
- Limit editing permissions and centralize rewrite rules in managed configurations.
- Restrict mod_proxy_ajp to trusted backends and monitor for anomalies.
- Configure limits for OCSP responses in environments using mod_md.
- Watch for unusual HTTP/2 traffic, repeated crashes, error spikes, or abnormal resource usage.
- Keep an accurate inventory of Apache deployments, including third-party systems and vendor-managed environments.
- Run vulnerability scans to confirm systems are fully patched and securely configured.
References
For more in-depth information about the recommendations, please visit the following links:
If you have any questions about this Cybersecurity Threat Advisory, don’t hesitate to get in touch with Barracuda Managed XDR’s Security Operations Center.
