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CVE-2026-42535 – DAV Property Database Manipulation and Denial of Service – Apache HTTP Server 2….

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Summary

CVE-2026-42535 is a critical path handling vulnerability in the mod_dav_fs module of Apache HTTP Server, affecting all versions through 2.4.67. The flaw is classified as CWE-668 (Exposure of Resource to Wrong Sphere) and allows a WebDAV content author to directly manipulate trusted DAV property databases and crash child processes. With a CVSS v3.1 score of 9.1 (Critical), the vulnerability is network-accessible, requires no privileges, and no user interaction, making internet-facing WebDAV-enabled Apache deployments a direct target.

Technical details

  • Root cause: A path handling flaw in mod_dav_fs (CWE-668: Exposure of Resource to Wrong Sphere) allows improperly resolved file paths to reach and modify trusted DAV property database files that should be inaccessible to content authors.
  • Trigger conditions: Exploitable on any Apache HTTP Server deployment where mod_dav_fs is loaded and WebDAV access is enabled; a WebDAV content author — including anonymous users on open WebDAV deployments — can issue crafted WebDAV requests to trigger the flaw.
  • Attack vector: Network-accessible (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction needed (UI:N).
  • Impact: Successful exploitation allows direct manipulation of trusted server-side DAV property databases (Integrity: High) and causes Apache child worker process crashes (Availability: High); there is no direct confidentiality impact (C:N).

Affected software

  • Apache HTTP Server versions 0 through 2.4.67 with mod_dav_fs (WebDAV) enabled

Severity

  • CVSS v3.1 Base Score: 9.1 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade to Apache HTTP Server 2.4.68, released June 8, 2026, which contains the fix (commit r1935013). This is the only vendor-recommended remediation; no alternative workarounds are offered.
  • If immediate patching is not possible, consider restricting access to WebDAV endpoints at the network perimeter or via Apache <Location> directives to limit exposure to trusted clients only.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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