In the Linux kernel, the following vulnerability has been resolved: net: ipv6: flowlabel: defer exclusive option free until RCU teardown `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU.

Metrics

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Key SSVC decision points have not yet been added.

Affected Vendors & Products

Vendors Products
Linux
  • Linux Kernel

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References
Link Providers
https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 cve-icon cve-icon
https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a cve-icon cve-icon
https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3 cve-icon cve-icon
https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4 cve-icon cve-icon
https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd cve-icon cve-icon
https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 cve-icon cve-icon
https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b cve-icon cve-icon
https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091 cve-icon cve-icon
History

Sat, 25 Apr 2026 09:00:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: net: ipv6: flowlabel: defer exclusive option free until RCU teardown `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU.
Title net: ipv6: flowlabel: defer exclusive option free until RCU teardown
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-04-25T08:46:56.807Z

Reserved: 2026-03-09T15:48:24.130Z

Link: CVE-2026-31680

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-04-25T09:16:01.673

Modified: 2026-04-25T09:16:01.673

Link: CVE-2026-31680

cve-icon Redhat

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