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Linux KernelOperating system · Linux

CVE-2026-53331

MEDIUM · 5.5 CVSS v3.1 Published 2026-07-01
Fix available
A fix is available. Upgrade to 5.15.210 / 6.1.176 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available 7 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: slimbus: qcom-ngd-ctrl: Avoid ABBA on tx_lock/ctrl->lock During the SSR/PDR down notification the tx_lock is taken with the intent to provide synchronization with active DMA transfers. But during this period qcom_slim_ngd_down() is invoked, which ends up in slim_report_absent(), which takes the slim_controller lock. In multiple other codepaths these two locks are taken in the opposite order (i.e. slim_controller then tx_lock). The result is a lockdep splat, and a possible deadlock: rprocctl/449 is trying to acquire lock: ffff00009793e620 (&ctrl->lock){+.+.}-{4:4}, at: slim_report_absent (drivers/slimbus/core.c:322) slimbus but task is already holding lock: ffff00009793fb50 (&ctrl->tx_lock){+.+.}-{4:4}, at: qcom_slim_ngd_ssr_pdr_notify (drivers/slimbus/qcom-ngd-ctrl.c:1475) slim_qcom_ngd_ctrl which lock already depends on the new lock. Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&ctrl->tx_lock); lock(&ctrl->lock); lock(&ctrl->tx_lock); lock(&ctrl->lock); The assumption is that the comment refers to the desire to not call qcom_slim_ngd_exit_dma() while we have an ongoing DMA TX transaction. But any such transaction is initiated and completed within a single qcom_slim_ngd_xfer_msg(). Prior to calling qcom_slim_ngd_exit_dma() the slim_controller is torn down, all child devices are notified that the slimbus is gone and the child devices are removed. Stop taking the tx_lock in qcom_slim_ngd_ssr_pdr_notify() to avoid the deadlock.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A lock ordering deadlock (ABBA) exists in the Linux kernel slimbus qcom-ngd-ctrl driver where tx_lock is acquired during SSR/PDR notification, then slim_report_absent() takes ctrl->lock - the reverse of other code paths. This creates a potential deadlock scenario. The fix removes the unnecessary tx_lock acquisition in qcom_slim_ngd_ssr_pdr_notify() since DMA transactions complete within a single xfer_msg() call and the controller is being torn down anyway.

MitigationApply the kernel patch that removes the tx_lock acquisition in qcom_slim_ngd_ssr_pdr_notify() to eliminate the deadlock, typically via kernel update or backporting the fix.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 5.11, < 5.15.210>= 5.16, < 6.1.176>= 6.2, < 6.6.143>= 6.7, < 6.12.94>= 6.13, < 6.18.36>= 6.19, < 7.0.13= 7.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check kernel version
    Run `uname -r` or check `/proc/version` to determine the running kernel version
    Affected if The kernel version falls within the affected ranges: >= 5.11 and < 5.15.210, >= 5.16 and < 6.1.176, >= 6.2 and < 6.6.143, >= 6.7 and < 6.12.94, >= 6.13 and < 6.18.36, >= 6.19 and < 7.0.13, or equals 7.1
  2. Verify qcom slimbus driver is loaded
    Check for slimbus controller driver presence via `lsmod | grep -i slim` or check device tree for qcom,slim-ngd compatible nodes in /sys/firmware/devicetree/base/
    Affected if The qcom-ngd-ctrl slimbus driver is present and managing slimbus devices on the system
  3. Locate driver source file
    Find the driver source at drivers/slimbus/qcom-ngd-ctrl.c in the kernel source tree or under /lib/modules/$(uname -r)/build/
    Affected if The driver source file exists on the system, indicating the affected driver is compiled into the kernel or as a module
  4. Check for vulnerable function
    Search for the function qcom_slim_ngd_ssr_pdr_notify in the driver source using `grep -n 'qcom_slim_ngd_ssr_pdr_notify' /path/to/qcom-ngd-ctrl.c`
    Affected if The function qcom_slim_ngd_ssr_pdr_notify exists in the driver, indicating the potentially vulnerable code path is present
  5. Inspect tx_lock usage in notify function
    Examine the function body of qcom_slim_ngd_ssr_pdr_notify for tx_lock acquisition (spin_lock calls) and compare lock ordering with other functions that use both tx_lock and ctrl->lock
    Affected if The function contains spin_lock(&ctrl->tx_lock) or similar tx_lock acquisition, creating potential ABBA deadlock with ctrl->lock acquired in other code paths

A system is affected if it runs a vulnerable kernel version within the specified ranges AND uses the qcom-ngd-ctrl slimbus driver with the tx_lock acquisition present in qcom_slim_ngd_ssr_pdr_notify().

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.15.210 / 6.1.176 / 6.6.143 or later
Fixed in 5.15.2106.1.1766.6.143
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch that removes the tx_lock acquisition in qcom_slim_ngd_ssr_pdr_notify() to eliminate the deadlock, typically via kernel update or backporting the fix.

Recommended fix High confidence

Linux kernel 5.15.210, 6.1.176, 6.6.143, or 6.12.94 (or any subsequent stable release)

  1. Identify the affected function qcom_slim_ngd_ssr_pdr_notify() in drivers/slimbus/qcom-ngd-ctrl.c
  2. Remove the tx_lock acquisition (spin_lock_irq/ spin_unlock_irq calls) around the qcom_slim_ngd_down() call in qcom_slim_ngd_ssr_pdr_notify()
  3. The justification is that DMA transactions are contained within a single qcom_slim_ngd_xfer_msg() call, so explicit synchronization at SSR/PDR down notification is unnecessary
  4. Apply the fix by editing the source file to remove the lock acquisition wrapper around the qcom_slim_ngd_down() invocation
  5. Rebuild the kernel with the updated driver

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

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Peer-ranked notes from engineers who’ve handled CVE-2026-53331 in production — separate from our analysis above.

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