CVE-2026-31680
net: ipv6: flowlabel: defer exclusive option free until RCU teardown
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.
INFO
Published Date :
April 25, 2026, 9:16 a.m.
Last Modified :
April 25, 2026, 9:16 a.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Affected Products
The following products are affected by CVE-2026-31680
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Defer freeing flowlabel option memory until RCU teardown.
- Ensure flowlabel option memory lifetime matches flowlabel object.
- Update kernel to include the fix.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-31680.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-31680 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-31680
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-31680 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-31680 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Apr. 25, 2026
Action Type Old Value New Value 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. Added Reference https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 Added Reference https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a Added Reference https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3 Added Reference https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4 Added Reference https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd Added Reference https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 Added Reference https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b Added Reference https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091