CVE-2026-31680
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.13%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.13% probability · 3th percentile
- CISA KEV
- Not listed
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827Patch
- https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342aPatch
- https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3Patch
- https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4Patch
- https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fdPatch
- https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8Patch
- https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249bPatch
- https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091Patch
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.