CVE-2025-71080
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-13

Last updated on: 2026-03-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT On PREEMPT_RT kernels, after rt6_get_pcpu_route() returns NULL, the current task can be preempted. Another task running on the same CPU may then execute rt6_make_pcpu_route() and successfully install a pcpu_rt entry. When the first task resumes execution, its cmpxchg() in rt6_make_pcpu_route() will fail because rt6i_pcpu is no longer NULL, triggering the BUG_ON(prev). It's easy to reproduce it by adding mdelay() after rt6_get_pcpu_route(). Using preempt_disable/enable is not appropriate here because ip6_rt_pcpu_alloc() may sleep. Fix this by handling the cmpxchg() failure gracefully on PREEMPT_RT: free our allocation and return the existing pcpu_rt installed by another task. The BUG_ON is replaced by WARN_ON_ONCE for non-PREEMPT_RT kernels where such races should not occur.
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Meta Information
Published
2026-01-13
Last Modified
2026-03-25
Generated
2026-06-16
AI Q&A
2026-01-14
EPSS Evaluated
2026-06-15
NVD
CVE-2025-71080
EUVD
EUVD-2026-2250
Affected Vendors & Products
Showing 11 associated CPEs
Vendor Product Version / Range
linux linux_kernel 6.12
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel From 6.13 (inc) to 6.18.4 (exc)
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel From 6.12.1 (inc) to 6.12.64 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-617 The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
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Executive Summary

This vulnerability occurs in the Linux kernel's IPv6 routing code on PREEMPT_RT kernels. After the function rt6_get_pcpu_route() returns NULL, the current task can be preempted, allowing another task on the same CPU to install a per-CPU routing entry (pcpu_rt). When the first task resumes, its attempt to install the route fails due to a race condition, triggering a BUG_ON error. The fix involves handling this race condition gracefully by freeing the allocation and returning the existing route instead of causing a BUG_ON, replacing it with a WARN_ON_ONCE for non-PREEMPT_RT kernels.

Impact Analysis

This vulnerability can cause kernel BUGs (crashes) on PREEMPT_RT Linux kernels due to a race condition in IPv6 routing code. This can lead to system instability or crashes, potentially affecting the availability and reliability of systems running affected kernels.

Mitigation Strategies

The vulnerability is fixed by updating the Linux kernel to a version that includes the patch for the BUG in rt6_get_pcpu_route() under PREEMPT_RT. Immediate mitigation involves applying the kernel update that handles the cmpxchg() failure gracefully and replaces the BUG_ON with WARN_ON_ONCE, preventing the BUG from triggering.

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