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 `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.

• linux linux kernel (>= 3.9 < 5.10.253) • linux linux kernel (>= 5.11 < 5.15.203) • linux linux kernel (>= 5.16 < 6.1.168) • linux linux kernel (>= 6.2 < 6.6.134) • linux linux kernel (>= 6.7 < 6.12.81) • linux linux kernel (>= 6.13 < 6.18.22) • linux linux kernel (>= 6.19 < 6.19.12) • linux linux kernel 7.0