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Vulnerabilities & Patches

Critical race‑condition flaw in Apache HTTP Server’s HTTP/2 module forces urgent patching

A high‑severity remote code execution bug in Apache’s HTTP/2 support affects versions 2.4.55‑2.4.70; administrators should upgrade to 2.4.71 immediately.

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Critical race‑condition flaw in Apache HTTP Server’s HTTP/2 module forces urgent patching

Security researchers have identified a severe concurrency bug in the HTTP/2 handling component of Apache HTTP Server that permits unauthenticated attackers to execute arbitrary code on vulnerable hosts. The defect resides in the routine that processes header information, where a timing weakness can corrupt heap structures and let an attacker run code under the web server account. Apache has shipped a fix for the bug, which is catalogued as CVE-2026-119618.

Scope of the vulnerability

The issue impacts Apache HTTP Server releases from 2.4.55 up to 2.4.70, as well as the accompanying mod_h2 library versions 2.0.8 through 2.0.42. The flaw is mitigated in the newly released 2.4.71 build, which contains a corrective change to the affected function.

Discovery and verification

Independent analysis by two separate research groups – one from Anthropic’s open‑source scanner and another from Google Cloud’s vulnerability team – first uncovered the problem. Red Hat later confirmed that the weakness can be leveraged remotely without any credentials.

Risk assessment and exposure

Industry monitoring indicates that a majority of cloud‑based deployments still run vulnerable versions, with roughly two‑thirds of surveyed environments affected and about half of those openly reachable from the internet. Wiz rates the flaw critical, though no official severity score is available yet and Wiz says it is not aware of public exploits or attacks. Exposure also depends on HTTP/2 being enabled, which is off by default.

Mitigation guidance for IT and security teams

  • Apply the official update: Upgrade all Apache HTTP Server instances to version 2.4.71 or later as soon as possible.
  • Temporarily disable HTTP/2: If immediate patching is not feasible, turn off the HTTP/2 module until the upgrade can be performed.
  • Review exposure: Scan internal and external assets to identify servers still running the affected releases, especially those exposed to the public internet.
  • Monitor for indicators: Look for unusual heap‑related crashes or unexpected process behavior that could hint at attempted exploitation.

Why it matters

Enterprises that rely on Apache for web services – including many Red Hat Enterprise Linux users and cloud providers – could see their servers hijacked, leading to data loss, service disruption, or further lateral movement within networks. Prompt remediation reduces the attack surface and protects both internal systems and external customers.

Sources

This brief was prepared with AI assistance from the sources above and reviewed by our editors.

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