CVE-2025-37882: Linux Kernel Race Condition Vulnerability

CVE-2025-37882 Overview

CVE-2025-37882 is a use-after-free vulnerability [CWE-416] in the Linux kernel's xHCI (Extensible Host Controller Interface) USB driver. The flaw resides in the handling of isochronous Ring Underrun and Ring Overrun events within drivers/usb/host/xhci-ring.c. On xHCI 1.1 and later host controllers, the TRB (Transfer Request Block) pointer of these events points at the enqueue position at the time of error, while older controllers report NULL. A race condition allows a new Transfer Descriptor (TD) to occupy the ring position before the event handler runs, causing premature TD completion and potential buffer use-after-free by the host controller.

Critical Impact
A local attacker with low privileges can trigger memory corruption in the Linux kernel USB subsystem, resulting in data loss, system instability, or potential privilege escalation through kernel memory buffer use-after-free.

Affected Products

Linux Kernel (multiple stable branches prior to the fix commits)
Systems using xHCI 1.1+ USB host controllers with isochronous devices
Distributions shipping affected kernel versions with USB isochronous transfer support

Discovery Timeline

2025-05-09 - CVE-2025-37882 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-37882

Vulnerability Analysis

The vulnerability affects the isochronous transfer event handling path in the xHCI driver. When the host controller generates a Ring Underrun or Ring Overrun event, the TRB pointer in the event references the enqueue position at the moment the error occurred. Between error occurrence and interrupt handler execution, the driver may queue a new TD at that same ring position.

When this race triggers after a Missed Service Error, the handler skips previously missed TDs and incorrectly processes the newly queued TD as if it matched the event. The TD can be completed and returned to its owning driver prematurely. The xHC controller may still write to the associated buffer after the memory has been freed or reassigned, producing a use-after-free condition [CWE-416].

Root Cause

The root cause is unsafe assumptions in the xrun event handler about TRB pointer validity and TD ordering. The handler completed TDs on xrun events without verifying that queued TDs matched the event's TRB pointer, which can legitimately be NULL, a link TRB, or a no-op TRB. Combined with the timing window between hardware event generation and software handling, this permits stale TRB pointers to reference freshly queued TDs.

Attack Vector

Exploitation requires local access with low privileges. The reporter demonstrated the race by raising interrupt moderation to increase IRQ handling delay. Natural system load producing similar interrupt latency can also trigger the condition. An attacker with control over USB isochronous transfers (audio, video, or similar devices) could deliberately induce timing conditions that surface the flaw, leading to kernel memory corruption.

The vulnerability manifests in the xHCI ring event handler when processing hardware-generated underrun and overrun events. No exploit code is publicly available for this issue. See the upstream commits referenced below for the corrected event handling logic.

Detection Methods for CVE-2025-37882

Indicators of Compromise

Kernel log warnings from the xHCI driver referencing TRB pointer mismatches or unexpected TD states
Unexplained USB isochronous device disconnects, audio glitches, or video capture failures preceding kernel crashes
Kernel oops or panic messages in dmesg referencing xhci_hcd, handle_tx_event, or use-after-free reports from KASAN-enabled kernels

Detection Strategies

Deploy KASAN (Kernel Address Sanitizer) builds in test environments to surface use-after-free reports in the xHCI ring handler
Monitor kernel version inventory across Linux endpoints to identify hosts running kernels prior to the patched commits
Review crash dumps from systems using USB audio, webcams, or other isochronous devices for xHCI-related backtraces

Monitoring Recommendations

Aggregate dmesg and journald logs centrally and alert on xHCI driver warnings or kernel oops events
Track kernel package versions across the fleet using configuration management telemetry
Correlate USB device error rates with kernel stability metrics on systems handling isochronous workloads

How to Mitigate CVE-2025-37882

Immediate Actions Required

Update the Linux kernel to a version containing the upstream fix commits 16a7a8e6c47f, 39a080a2925c, or 906dec15b9b3 as backported by your distribution
Prioritize patching multi-user systems, shared workstations, and hosts where untrusted users can access USB isochronous devices
Reboot systems after kernel package updates to activate the fixed driver

Patch Information

The fix is available in the upstream Linux kernel through the following commits: Linux Kernel Commit 16a7a8e, Linux Kernel Commit 39a080a, and Linux Kernel Commit 906dec1. The patches modify the xHCI ring event handler to avoid completing TDs on xrun events, suppress warnings when queued TDs do not match the event's TRB pointer, and safely handle xrun events when the skip flag is clear.

Workarounds

Restrict physical access to USB ports on affected systems where kernel updates cannot be applied immediately
Disable or unload the xhci_hcd module on systems that do not require USB 3.x functionality, understanding this removes USB host controller support
Avoid workloads that stress USB isochronous transfers on unpatched systems until updates are applied

bash

# Verify running kernel version and check for xHCI patch presence
uname -r

# On Debian/Ubuntu systems, update the kernel package
sudo apt update && sudo apt upgrade linux-image-$(uname -r | cut -d- -f3-)

# On RHEL/Rocky/Alma systems
sudo dnf update kernel

# Reboot to activate the patched kernel
sudo systemctl reboot