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7.8 High

CVE-2026-31680 In the Linux kernel, the following vulnerability has been resolved: net: ipv6: flowlabel: defer exclusive option free…

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.

Affected products and versions

Product Affected versions Fixed in
Linux 7.0 earliest → < 7.0 7.0
Linux 6.19 earliest → < 6.19.12 6.19.12
Linux 6.18 earliest → < 6.18.22 6.18.22
Linux 6.12 earliest → < 6.12.81 6.12.81
Linux 6.6 earliest → < 6.6.134 6.6.134
Linux 6.1 earliest → < 6.1.168 6.1.168
Linux 5.15 earliest → < 5.15.203 5.15.203
Linux 5.10 earliest → < 5.10.253 5.10.253
Linux 3.9 No fix stated
Show the 3 other branches
Product Affected versions Fixed in
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP 3.1 3.1.7 → latest No fix stated

References

Timeline

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