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VulnerabilityPublished Updated

CVE-2026-52947: Linux kernel · Race Condition

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.8 High · fixed in ab269990ed58143a92a263be1bee626d82ac03da : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:30 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in ab269990ed58143a92a263be1bee626d82ac03da, a2171131ecda1ed61a594a1eb715e75fdad0fef5, 474293d90880622fde9d2430fb0165767090f7b3 +5
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ bdabad3e363d825ddf9679dd431cca0b2c30f881, < ab269990ed58143a92a263be1bee626d82ac03da
Fixed in
  • ab269990ed58143a92a263be1bee626d82ac03da
LinuxLinuxAffected
  • ≥ bdabad3e363d825ddf9679dd431cca0b2c30f881, < a2171131ecda1ed61a594a1eb715e75fdad0fef5
Fixed in
  • a2171131ecda1ed61a594a1eb715e75fdad0fef5
LinuxLinuxAffected
  • ≥ bdabad3e363d825ddf9679dd431cca0b2c30f881, < 474293d90880622fde9d2430fb0165767090f7b3
Fixed in
  • 474293d90880622fde9d2430fb0165767090f7b3
LinuxLinuxAffected
  • ≥ bdabad3e363d825ddf9679dd431cca0b2c30f881, < 2047c2aa0963bb2872fd722300a15bcb441a4c00
Fixed in
  • 2047c2aa0963bb2872fd722300a15bcb441a4c00
LinuxLinuxAffected
  • ≥ bdabad3e363d825ddf9679dd431cca0b2c30f881, < 7de2d447072be3b1a76793f034432338fc9c494b
Fixed in
  • 7de2d447072be3b1a76793f034432338fc9c494b
LinuxLinuxAffected
  • ≥ bdabad3e363d825ddf9679dd431cca0b2c30f881, < 03bfa95e452e2b6ccd76a332060ae4feaf5ad84d
Fixed in
  • 03bfa95e452e2b6ccd76a332060ae4feaf5ad84d

Description

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.)

References

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