CVE-2026-98596
Received Received - Intake

Linux kernel IPv6 dst leak in uncached routes

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ipv6: Fix dst leak for uncached routes. ip6_route_output_flags(), ip6_rt_put_flags(), and ip6_dst_check() detect an uncached route by list_empty(&rt->dst.rt_uncached), which replaced the static DST_NOCACHE flag check in commit a4c2fd7f7891 ("net: remove DST_NOCACHE flag"). When a device is unregistered, rt6_uncached_list_flush_dev() unlinks uncached routes tied to the device from rt6_uncached_list. Previously, they were moved to another list with list_move() (__list_del_entry() + list_add()), and since commit 98aa546af5e4 ("inet: remove (struct uncached_list)->quarantine"), the routes are just unlinked with list_del_init(). If list_del_init() runs concurrently, list_empty() evaluates to true; ip6_route_output_flags() calls dst_hold_safe() incorrectly and ip6_rt_put_flags() skips ip6_rt_put(), leaking dst, and thus dev tied via rt->from as well. The same race is partially fixed by commit 9a6f0c4d5796 ("dst: fix races in rt6_uncached_list_del() and rt_del_uncached_list()"). Let's check rt6->dst.rt_uncached_list instead. Note that IPv4 does not have the same issue.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98596
EUVD
EUVD-2026-103641

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
Linux Linux 98aa546af5e4f180439c82da403cc77926d3953b
Linux Linux 98aa546af5e4f180439c82da403cc77926d3953b
Linux Linux 98aa546af5e4f180439c82da403cc77926d3953b
Linux Linux 98aa546af5e4f180439c82da403cc77926d3953b
Linux Linux 6.11

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a race condition in IPv6 route handling. When a device is unregistered, uncached routes tied to it are improperly handled due to concurrent list operations. This causes the kernel to incorrectly evaluate route states, leading to memory leaks of destination (dst) structures and associated device references.

Detection Guidance

This vulnerability is specific to the Linux kernel's IPv6 routing and requires kernel-level inspection. Detection involves checking for kernel versions affected by the issue and verifying if the race condition in dst handling exists. Commands like uname -a to check kernel version and examining kernel logs for related errors may help. No direct commands are provided in the context to detect this specific race condition.

Impact Analysis

This vulnerability could lead to system instability or crashes due to memory leaks. It may also cause network connectivity issues if routes are not properly managed. Systems relying on IPv6 networking could experience performance degradation or unexpected behavior.

Mitigation Strategies

Apply the latest kernel patches that address this issue. Since the vulnerability is resolved in a specific kernel commit, updating to a patched kernel version is the primary mitigation. Monitor vendor advisories for kernel updates and apply them promptly. No additional steps are specified in the context.

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