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CVE-2026-31680

net: ipv6: flowlabel: defer exclusive option free until RCU teardown

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From d3aedd5ebd4b0b925b0bcda548066803e1318499 · fixed in 4b6798024f7b2d535f3db1002c760143cdbd1bd3; From d3aedd5ebd4b0b925b0bcda548066803e1318499 · fixed in 3c54b66c83fb8fcbde8e6a7bf90b65856e39f827; From d3aedd5ebd4b0b925b0bcda548066803e1318499 · fixed in 5a6b15f861b7c1304949e3350d23490a5fe429fd; From d3aedd5ebd4b0b925b0bcda548066803e1318499 · fixed in 6c7fbdb8ffde6413640de7cfbd7c976c353e89f8; From d3aedd5ebd4b0b925b0bcda548066803e1318499 · fixed in 8027964931785cb73d520ac70a342a3dc16c249b; From d3aedd5ebd4b0b925b0bcda548066803e1318499 · fixed in 414726b69921fe6355ae453f5b35e68dd078342a; From d3aedd5ebd4b0b925b0bcda548066803e1318499 · fixed in 572ce62778519a7d4d1c15f55dd2e45a474133c4; From d3aedd5ebd4b0b925b0bcda548066803e1318499 · fixed in 9ca562bb8e66978b53028fa32b1a190708e6a091

  • Linux Linux

    3.9

  • KernelLinux

    From 3.9.0 · fixed in 5.10.253; From 5.11.0 · fixed in 5.15.203; From 5.16.0 · fixed in 6.1.168; From 6.2.0 · fixed in 6.6.134; From 6.7.0 · fixed in 6.12.81; From 6.13.0 · fixed in 6.18.22; From 6.19.0 · fixed in 6.19.12

References 8

git.kernel.org