CVE-2025-49180: RandR Extension Buffer Overflow Flaw

CVE-2025-49180 Overview

CVE-2025-49180 is an integer overflow vulnerability [CWE-190] in the X.Org Server RandR extension. The RRChangeProviderProperty function fails to properly validate input when computing the total size to allocate for provider properties. A local, authenticated attacker can trigger the overflow to cause memory corruption in the X server process.

Because the X server historically runs with elevated privileges, successful exploitation can lead to confidentiality, integrity, and availability impact on the host. The flaw was disclosed by Red Hat and patched upstream in the xorg/xserver project on freedesktop.org.

Critical Impact
Local attackers can trigger memory corruption in the X server via a malformed RandR provider property request, potentially leading to code execution or privilege escalation on affected Linux desktops.

Affected Products

X.Org Server (xorg-server) versions prior to the upstream fix in commit 3c3a4b7
Red Hat Enterprise Linux distributions covered by RHSA-2025:9303 through RHSA-2025:10410
Debian LTS distributions referenced in the June 2025 Debian LTS announcement

Discovery Timeline

2025-06-17 - CVE-2025-49180 published to NVD
2025-06 - Debian LTS advisory published
2026-06-30 - Last updated in NVD database

Technical Details for CVE-2025-49180

Vulnerability Analysis

The vulnerability resides in RRChangeProviderProperty, part of the RandR (Resize and Rotate) X server extension that manages display providers and their associated properties. The function computes an allocation size based on client-supplied parameters such as property length and item format. Without proper bounds validation, arithmetic on these values wraps past the maximum representable integer.

The undersized allocation is then used to store client-controlled data, resulting in a heap buffer overflow. Because RandR requests are accepted from any client connected to the X server, any local user with access to the display can send the crafted request. The X server process, which frequently runs with root privileges on traditional Linux desktops, then processes the malformed data in-process.

Root Cause

The root cause is unchecked arithmetic when calculating the size of a memory buffer intended to hold the provider property payload. Multiplication of the property length by the per-item size produces a value larger than the platform's integer width can hold, wrapping to a small value. The subsequent allocation succeeds but reserves fewer bytes than the caller intends to write, and the following copy operation overflows adjacent heap memory. This matches the classic [CWE-190] integer overflow to buffer overflow pattern.

Attack Vector

Exploitation requires local access and a valid X server connection. An authenticated user submits a crafted RandR request containing property length and format values chosen to trigger the arithmetic wrap. The X server allocates a truncated buffer, writes attacker-controlled bytes past the end, and corrupts heap metadata or adjacent objects. Standard heap grooming techniques can then be used to convert the corruption into arbitrary code execution within the X server context. No user interaction beyond the attacker's own session is required. See the Freedesktop Git Commit 3c3a4b7 for the corrected size computation logic.

Detection Methods for CVE-2025-49180

Indicators of Compromise

Unexpected crashes or restarts of the Xorg process on multi-user or shared Linux hosts
Core dumps referencing RRChangeProviderProperty or nearby RandR handlers
dmesg or journald entries reporting segmentation faults in Xorg originating from unprivileged user sessions
Local user processes issuing RandR provider property requests outside of normal desktop session activity

Detection Strategies

Inventory installed xorg-server package versions across Linux endpoints and compare against the fixed builds referenced in the Red Hat and Debian advisories.
Monitor process telemetry for Xorg termination signals correlated with local user activity, then pivot to the parent session for triage.
Enable audit rules on X server binaries and shared libraries to flag unexpected modification or reload behavior after a crash.

Monitoring Recommendations

Ingest /var/log/Xorg.*.log, journald, and audit logs into a central analytics platform and alert on repeated Xorg crashes from non-administrative users.
Track successful package updates for xorg-x11-server and xserver-xorg-core to confirm remediation coverage across the fleet.
Correlate local privilege escalation indicators (new SUID files, unexpected root shells) with prior X server instability on the same host.

How to Mitigate CVE-2025-49180

Immediate Actions Required

Apply the vendor-supplied xorg-server updates from your Linux distribution as soon as they are available.
Prioritize multi-user systems, jump hosts, and workstations where untrusted local users can open X sessions.
Restart the display manager or reboot affected hosts after patching so the vulnerable X server process is replaced.

Patch Information

The upstream fix is available in the X.Org Server repository as commit 3c3a4b7, which adds proper size validation to RRChangeProviderProperty. Red Hat has shipped fixes across the RHSA-2025:9303, RHSA-2025:9304, RHSA-2025:9305, RHSA-2025:9306, RHSA-2025:9392, RHSA-2025:9964, and the RHSA-2025:10258 through RHSA-2025:10410 series of advisories. Debian users should apply the packages announced in the Debian LTS Announcement 2025/06. Refer to the Red Hat CVE Reference CVE-2025-49180 for the authoritative list of fixed package versions per platform.

Workarounds

Restrict local login on shared systems to trusted users until patches are deployed.
Prefer Wayland-based sessions where feasible, since the vulnerable code path is specific to the X.Org Server RandR extension.
Where the X server can be run rootless (for example, Xorg.wrap with needs_root_rights = no), enable that configuration to reduce blast radius of any memory corruption.

bash

# Example: verify the installed xorg-server version on RHEL and Debian-based systems
rpm -q xorg-x11-server-Xorg        # RHEL / Fedora
dpkg -l xserver-xorg-core          # Debian / Ubuntu

# Confirm the update from the relevant advisory has been applied, then restart the session
sudo systemctl restart gdm         # or lightdm / sddm depending on the display manager