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Linux KernelOperating system · Linux

CVE-2026-52947

HIGH · 7.8 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 →
80/100
Remediation priority · High
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: net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove In qrtr_port_remove(), the socket reference count is decremented via __sock_put() before the port is removed from the qrtr_ports XArray and before the RCU grace period elapses. This breaks the fundamental RCU update paradigm. It exposes a race window where a concurrent RCU reader (such as qrtr_reset_ports() or qrtr_port_lookup()) can obtain a pointer to the socket from the XArray, and attempt to call sock_hold() on a socket whose reference count has already dropped to zero. This exact race condition was hit during syzkaller fuzzing, leading to the following refcount saturation warning and a potential Use-After-Free: refcount_t: saturated; leaking memory. WARNING: CPU: 3 PID: 1273 at lib/refcount.c:22 refcount_warn_saturate+0xae/0x1d0 Modules linked in: qrtr(+) bochs drm_shmem_helper ... Call Trace: <TASK> qrtr_reset_ports net/qrtr/af_qrtr.c:768 [inline] [qrtr] __qrtr_bind.isra.0+0x48b/0x570 net/qrtr/af_qrtr.c:805 [qrtr] qrtr_bind+0x17d/0x210 net/qrtr/af_qrtr.c:901 [qrtr] kernel_bind+0xe4/0x120 net/socket.c:3592 qrtr_ns_init+0x1a6/0x380 net/qrtr/ns.c:715 [qrtr] qrtr_proto_init+0x3b/0xff0 net/qrtr/af_qrtr.c:169 [qrtr] do_one_initcall+0xf5/0x5e0 init/main.c:1283 ... </TASK> Fix this by deferring the reference count decrement until after the xa_erase() and the synchronize_rcu() complete. (Note: The v1 of this patch incorrectly replaced __sock_put() with sock_put(). As Simon Horman pointed out, the callers of qrtr_port_remove() still hold a reference to the socket, so freeing the socket memory here would lead to a subsequent UAF in the caller. Thus, the __sock_put() is kept, but only repositioned to close the RCU race.)

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

In the Linux kernel's QRTR (Qualcomm IPC Router) subsystem, qrtr_port_remove() incorrectly calls __sock_put() to decrement the socket reference count before removing the port from the XArray and before the RCU grace period elapses. This violates RCU semantics and creates a race window where concurrent RCU readers (qrtr_reset_ports() or qrtr_port_lookup()) can obtain a pointer to a socket whose refcount has already dropped to zero, causing refcount saturation and potential Use-After-Free.

MitigationApply the kernel patch that moves __sock_put() to after xa_erase() and synchronize_rcu() complete, then update affected systems to the patched kernel version.

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:>= 4.7, < 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

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
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 against affected ranges
    Run 'uname -r' or 'cat /proc/version' to get the kernel version, then compare against: >= 4.7, < 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
    Affected if The installed kernel version falls within any of the listed vulnerable ranges
  2. Verify QRTR subsystem is built into the kernel
    Check if CONFIG_QRTR and CONFIG_QRTR_TUNNEL are set in kernel config: 'cat /boot/config-$(uname -r) | grep -E "CONFIG_QRTR"' or check /proc/config.gz if available
    Affected if QRTR support is compiled into the running kernel (CONFIG_QRTR=m or =y)
  3. Confirm qrtr_port_remove function exists in kernel
    Search for the vulnerable function in kernel symbols: 'grep -r "qrtr_port_remove" /boot/System.map-$(uname -r) 2>/dev/null || cat /proc/kallsyms | grep qrtr_port_remove'
    Affected if The function qrtr_port_remove is present in the kernel symbol table
  4. Verify the RCU race condition exists in source code
    If kernel source is available, inspect net/qrtr/smd.c or net/qrtr/af_qrtr.c for the qrtr_port_remove function - check if __sock_put() is called before xa_erase() without synchronize_rcu() in between
    Affected if The source code shows __sock_put() called before xa_erase() without the intervening synchronize_rcu() that the fix introduces

You are affected if your kernel version is in the vulnerable ranges AND the QRTR subsystem is enabled, because only then can the RCU race in qrtr_port_remove be triggered.

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 moves __sock_put() to after xa_erase() and synchronize_rcu() complete, then update affected systems to the patched kernel version.

Recommended fix High confidence

5.10.259, 5.15.210, 6.1.176, or 6.6.143 (depending on your current branch)

  1. Upgrade the Linux kernel to version 5.10.259 or later if running 5.10.x
  2. Upgrade the Linux kernel to version 5.15.210 or later if running 5.11-5.15.x
  3. Upgrade the Linux kernel to version 6.1.176 or later if running 5.16-6.1.x
  4. Upgrade the Linux kernel to version 6.6.143 or later if running 6.2-6.6.x
  5. After upgrading, verify the fix is present by checking that qrtr_port_remove() calls __sock_put() after xa_erase() and synchronize_rcu()
Caveat Standard kernel upgrade considerations apply - review release notes for your distribution

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
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,520
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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

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-52947 in production — separate from our analysis above.

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What this is

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What belongs here
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