7

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2023-5574

CVE-2023-5574: A use-after-free flaw was found in xorg-x11-server-Xvfb. This issue occurs in Xvfb with a very...

A use-after-free flaw was found in xorg-x11-server-Xvfb. This issue occurs in Xvfb with a very specific and legacy configuration (a multi-screen setup with multiple protocol screens, also known as Zaphod mode). If the pointer is warped from a screen 1 to a screen 0, a use-after-free issue may be triggered during shutdown or reset of the Xvfb server, allowing for possible escalation of privileges or denial of service.

(GitHub Advisory)

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CVE-2023-5574

CVE-2023-5574:

7

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

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Root Cause Analysis

The vulnerability CVE-2023-5574 describes a use-after-free in xorg-x11-server-Xvfb during shutdown/reset in a multi-screen (Zaphod) configuration. The X.Org Security Advisory specifically mentions a 'Use-after-free bug in DamageDestroy'. Analysis of the GitLab merge request (MR #1189) associated with the fix for this CVE revealed two key commits addressing UAFs in screen cleanup: one in DamageDestroy (damageext/damageext.c) and another in the generic CloseScreen (dix/dispatch.c). Both functions are critical to screen resource deallocation. The commit messages and code changes indicate that improper management of devPrivates (private data associated with damage objects or screens) in these functions led to the UAF conditions. The fix for CloseScreen explicitly mentions the problematic interaction with Xvfb in Zaphod mode and the damage extension, aligning perfectly with the CVE description. Therefore, both DamageDestroy and CloseScreen, in their pre-patch states, are identified as the vulnerable functions.

Vulnerable functions

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WAF Rule

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Reasoning

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