High 7.8Published Apr 25, 2026

CVE-2026-31680net: ipv6: flowlabel: defer exclusive option free until RCU teardown

Updated under an hour ago (Oct 27, 2026, 5:00 PM ET)

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Exploited in the last 30 days

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: 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-416
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 19, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from d3aedd5ebd4b0b925b0bcda548066803e1318499 before 4b6798024f7b2d535f3db1002c760143cdbd1bd3; from d3aedd5ebd4b0b925b0bcda548066803e1318499 before 3c54b66c83fb8fcbde8e6a7bf90b65856e39f827; from d3aedd5ebd4b0b925b0bcda548066803e1318499 before 5a6b15f861b7c1304949e3350d23490a5fe429fd; from d3aedd5ebd4b0b925b0bcda548066803e1318499 before 6c7fbdb8ffde6413640de7cfbd7c976c353e89f8; from d3aedd5ebd4b0b925b0bcda548066803e1318499 before 8027964931785cb73d520ac70a342a3dc16c249b; from d3aedd5ebd4b0b925b0bcda548066803e1318499 before 414726b69921fe6355ae453f5b35e68dd078342a; from d3aedd5ebd4b0b925b0bcda548066803e1318499 before 572ce62778519a7d4d1c15f55dd2e45a474133c4; from d3aedd5ebd4b0b925b0bcda548066803e1318499 before 9ca562bb8e66978b53028fa32b1a190708e6a091	CNA record
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
linux linux_kernel linux:linux_kernel	from 3.9 before 5.10.253; from 5.11 before 5.15.203; from 5.16 before 6.1.168; from 6.2 before 6.6.134; from 6.7 before 6.12.81; from 6.13 before 6.18.22; from 6.19 before 6.19.12; 7.0; and 5 more ranges	NVD

References

References

https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3	patch
https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827	patch
https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd	patch
https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8	patch
https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b	patch
https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a	patch
https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4	patch
https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091	patch
https://cert-portal.siemens.com/productcert/html/ssa-019113.html
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
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The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.