CVE-2026-97940
Received Received - Intake

Use-After-Free in Linux Kernel IPv6 Route Walker

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ipv6: fix fib6 walker UAF on seq stop ipv6_route_iter_active() treats a walker in FWS_U at the table root as already unlinked. fib6_del_route() can move a still-linked walker into that same state when the current leaf is the last route at the root, so ipv6_route_native_seq_stop() skips fib6_walker_unlink(). The seq private object can then be freed while it remains on net->ipv6.fib6_walkers. A later route deletion walks the dangling list and uses the freed walker. Use the list head as membership state and reinitialize it when unlinking. Keep the existing w->node check so a never-started iterator with a zeroed private object is not treated as linked. The same stop helper is used by /proc/net/ipv6_route and by the BPF ipv6_route iterator. The BPF show path only widens the race.

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-97940
EUVD
EUVD-2026-86794

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a use-after-free (UAF) vulnerability in the Linux kernel's IPv6 routing subsystem. It occurs when a walker object is incorrectly treated as unlinked while still being part of a list, leading to a dangling pointer. When the walker is later accessed, it can cause memory corruption or crashes.

Detection Guidance

This vulnerability is specific to the Linux kernel's IPv6 routing implementation and may not have direct detection commands. Monitor kernel logs for crashes or errors related to IPv6 routing or fib6 walkers. Check for kernel panics or segmentation faults in processes handling IPv6 routes.

Impact Analysis

This vulnerability could allow an attacker to cause a denial-of-service (system crash) or potentially execute arbitrary code with kernel privileges. It affects systems running vulnerable Linux kernels, especially those using IPv6 routing features.

Mitigation Strategies

Update the Linux kernel to the latest stable version that includes the fix for this vulnerability. If immediate patching is not possible, consider disabling IPv6 routing features temporarily or restricting access to IPv6 route manipulation tools until the kernel is updated.

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