Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-63942 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions f3378b0d7bd4605de89b083b2900788157a181cc, 290f515c5e3b3900bc2fe24f179999fd08d23bfa, d16548be2ea5058227d79799e81dab61c9bca8ec as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to f3378b0d7bd4605de89b083b2900788157a181cc or 290f515c5e3b3900bc2fe24f179999fd08d23bfa or d16548be2ea5058227d79799e81dab61c9bca8ec or 15b1723c1472e802f9f7e69ae4e64f7dbf588848, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.259 or 5.15.210 or 6.1.176 or 6.6.143, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 6fa45a22689722dac9f0e90c0931d4b34b334ede up to, but not including, f3378b0d7bd4605de89b083b2900788157a181cc; 6fa45a22689722dac9f0e90c0931d4b34b334ede up to, but not including, 290f515c5e3b3900bc2fe24f179999fd08d23bfa; 6fa45a22689722dac9f0e90c0931d4b34b334ede up to, but not including, d16548be2ea5058227d79799e81dab61c9bca8ec; 6fa45a22689722dac9f0e90c0931d4b34b334ede up to, but not including, 15b1723c1472e802f9f7e69ae4e64f7dbf588848; 6fa45a22689722dac9f0e90c0931d4b34b334ede up to, but not including, 51026cff1f4f3b762a0b5a07c727bd59cef45320; 6fa45a22689722dac9f0e90c0931d4b34b334ede up to, but not including, 74d6aae1df45d3414178986be743f946988fddf6; 6fa45a22689722dac9f0e90c0931d4b34b334ede up to, but not including, a1e81b58da0179531bedf0b9f2811f5f992d5c4b; 6fa45a22689722dac9f0e90c0931d4b34b334ede up to, but not including, ef15ccbb3e8640a723c42ad90eaf81d66ae02017; and 1 more ranges | f3378b0d7bd4605de89b083b2900788157a181cc, 290f515c5e3b3900bc2fe24f179999fd08d23bfa, d16548be2ea5058227d79799e81dab61c9bca8ec, 15b1723c1472e802f9f7e69ae4e64f7dbf588848, 51026cff1f4f3b762a0b5a07c727bd59cef45320, 74d6aae1df45d3414178986be743f946988fddf6 |
| Linux | Linux Kernel | 4.2 up to, but not including, 5.10.259; 5.11 up to, but not including, 5.15.210; 5.16 up to, but not including, 6.1.176; 6.2 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.1 | 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
How developers prevent this class of flaw
- In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
- Use thread-safe capabilities such as the data access abstraction in Spring.
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/15b1723c1472e802f9f7e69ae4e64f7dbf588848
- git.kernel.org/stable/c/290f515c5e3b3900bc2fe24f179999fd08d23bfa
- git.kernel.org/stable/c/51026cff1f4f3b762a0b5a07c727bd59cef45320
- git.kernel.org/stable/c/74d6aae1df45d3414178986be743f946988fddf6
- git.kernel.org/stable/c/a1e81b58da0179531bedf0b9f2811f5f992d5c4b
- git.kernel.org/stable/c/d16548be2ea5058227d79799e81dab61c9bca8ec
- git.kernel.org/stable/c/ef15ccbb3e8640a723c42ad90eaf81d66ae02017
- git.kernel.org/stable/c/f3378b0d7bd4605de89b083b2900788157a181cc
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
Spotted an error? Tell us.