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Linux KernelOperating system · Linux

CVE-2026-52946

HIGH · 7.5 CVSS v3.1 Published 2026-06-24
Fix available
A fix is available. Upgrade to 5.10.259 / 5.15.210 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click 8 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: fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling A SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in send_sigio() and send_sigurg() when a process group receives a signal. When FASYNC is configured for a process group (PIDTYPE_PGID), both functions use read_lock(&tasklist_lock) to traverse the task list. However, they are frequently called from softirq context: - send_sigio() via input_inject_event -> kill_fasync - send_sigurg() via tcp_check_urg -> sk_send_sigurg (NET_RX_SOFTIRQ) The deadlock is caused by the rwlock writer fairness mechanism: 1. CPU 0 (process context) holds read_lock(&tasklist_lock) in do_wait(). 2. CPU 1 (process context) attempts write_lock(&tasklist_lock) in fork() or exit() and spins, which blocks all new readers. 3. CPU 0 is interrupted by a softirq (e.g., TCP URG packet reception). 4. The softirq calls send_sigurg() and attempts to acquire read_lock(&tasklist_lock), deadlocking because CPU 1 is waiting. Since PID hashing and do_each_pid_task() traversals are already RCU-protected, the read_lock on tasklist_lock is no longer strictly required for safe traversal. Fix this by replacing tasklist_lock with rcu_read_lock(), aligning the process group signaling path with the single-PID path. This also mitigates a potential remote denial of service vector via TCP URG packets. Lockdep splat: ===================================================== WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected [...] Chain exists of: &dev->event_lock --> &f_owner->lock --> tasklist_lock Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(tasklist_lock); local_irq_disable(); lock(&dev->event_lock); lock(&f_owner->lock); <Interrupt> lock(&dev->event_lock); *** 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 deadlock vulnerability exists in the Linux kernel's FASYNC signal handling for process groups. The send_sigio() and send_sigurg() functions use read_lock(&tasklist_lock) while being callable from softirq context (NET_RX_SOFTIRQ). When a writer is waiting for tasklist_lock, the rwlock fairness mechanism blocks readers, causing a deadlock when a process context holds the read lock and is interrupted by a softirq needing the same lock. The fix replaces the tasklist_lock with rcu_read_lock() since RCU already protects the pid task traversals.

MitigationApply the kernel patch that replaces tasklist_lock with rcu_read_lock() in send_sigio() and send_sigurg() for PIDTYPE_PGID. This aligns the process group signaling path with the single-PID path and eliminates the SOFTIRQ-unsafe lock dependency.

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:>= 2.6.12.1, < 5.10.259>= 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, < 7.1.1= 2.6.12

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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 'cat /proc/version' to get the running kernel version
    Affected if The kernel version falls within any of these ranges: >= 2.6.12.1 and < 5.10.259; >= 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; >= 7.1 and < 7.1.1; = 2.6.12
  2. Verify fasync support is enabled
    Check kernel config for CONFIG_FASYNC or look for loaded modules using fasync (e.g., 'lsmod' and check for drivers that use fasync, or inspect /proc/misc for fasync-related entries)
    Affected if The kernel was built with fasync support and the system uses any userspace applications or drivers that employ F_SETOWN/F_SETSIG fcntl operations for asynchronous I/O notification
  3. Confirm vulnerable code path exists in send_sigio
    Use 'grep -r "send_sigio" /boot/System.map-*' to locate the function address, then disassemble or check source for 'read_lock(&tasklist_lock)' usage in that function, or use 'objdump -d /boot/vmlinux-* | grep -A50 send_sigio'
    Affected if The kernel binary contains send_sigio() that uses read_lock(&tasklist_lock) for PIDTYPE_PGID paths
  4. Confirm vulnerable code path exists in send_sigurg
    Same method as step 3 but search for send_sigurg() function
    Affected if The kernel binary contains send_sigurg() that uses read_lock(&tasklist_lock) for PIDTYPE_PGID paths

The system is affected if it runs a kernel version within the affected ranges AND uses fasync operations (F_SETOWN/F_SETSIG) for process group signal delivery, which triggers the vulnerable code paths in send_sigio/send_sigurg.

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 5.10.259 / 5.15.210 / 6.1.176 or later
Fixed in 5.10.2595.15.2106.1.176
Interim mitigation

Apply the kernel patch that replaces tasklist_lock with rcu_read_lock() in send_sigio() and send_sigurg() for PIDTYPE_PGID. This aligns the process group signaling path with the single-PID path and eliminates the SOFTIRQ-unsafe lock dependency.

Recommended fix High confidence

Linux Kernel 5.10.259, 5.15.210, 6.1.176, or 6.6.143 (or later stable releases in each respective branch)

  1. Identify the currently running Linux kernel version using `uname -r`
  2. Determine which version range your current kernel falls into based on the affected ranges: >= 2.6.12.1 and < 5.10.259, >= 5.11 and < 5.15.210, >= 5.16 and < 6.1.176, or >= 6.2 and < 6.6.143
  3. Upgrade to a patched kernel version: for 5.10.x branch upgrade to >= 5.10.259, for 5.11-5.15.x upgrade to >= 5.15.210, for 5.16-6.1.x upgrade to >= 6.1.176, for 6.2-6.6.x upgrade to >= 6.6.143
  4. After kernel upgrade, reboot the system to load the fixed kernel
  5. Verify the fix is applied by checking the kernel version and reviewing the fcntl.c changes in the kernel source if needed using `grep -A 20 'fasync' fs/fcntl.c`
Caveat Kernel upgrades may require rebuild of out-of-tree kernel modules and should be tested in a non-production environment first; some older hardware drivers may not be compatible with newer kernels

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

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing8.0 h
  • Review / QA5.0 h
20.0 hours of engineering $3,440
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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-2026-52946 in production — separate from our analysis above.

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