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CVE-2026-93226

Linux: ipv6: use RCU iterator to dump route exceptions

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.18%Chance of exploitation activity in the next 30 days, higher than 6% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in6bd3f94ed858f2d072627546b4cdf712b0f8ea88Also 9c6be625e1a7258e845d6193b3b6b084a00f8e9e, 3665abc3d2ae8a78cb67f858e848481432ec75db and 1 moreCVE List
Published24 Sep 2026Updated 19 Oct 2026CVE List

What fixes it

  • 6bd3f94ed858f2d072627546b4cdf712b0f8ea88LinuxCVE List
  • 9c6be625e1a7258e845d6193b3b6b084a00f8e9eLinuxCVE List
  • 3665abc3d2ae8a78cb67f858e848481432ec75dbLinuxCVE List
  • 47cdab0d51aaa9bd85f8e4904585bd5bd4df4488LinuxCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

In the Linux kernel, the following vulnerability has been resolved:

ipv6: use RCU iterator to dump route exceptions

rt6_nh_dump_exceptions() uses hlist_for_each_entry() to iterate over RCU-protected exception lists. The caller holds rcu_read_lock(), but does not hold rt6_exception_lock, so rt6_insert_exception() can concurrently add an entry with hlist_add_head_rcu().

KCSAN reports this race (irrelevant details omitted):

================================================================== BUG: KCSAN: data-race in rt6_insert_exception / rt6_nh_dump_exceptions

write (marked) to 0xffff8a7c44c59620 of 8 bytes by interrupt on cpu 5: rt6_insert_exception+0x3bb/0x760 __ip6_rt_update_pmtu+0x4fe/0x750 ip6_sk_update_pmtu+0x19a/0x3b0 udpv6_err+0x3ff/0x800 icmpv6_notify+0x1e1/0x440 icmpv6_rcv+0x8c0/0xab0 ip6_protocol_deliver_rcu+0x616/0x840 ip6_input_finish+0xb9/0x160 ... entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8a7c44c59620 of 8 bytes by task 549 on cpu 14: rt6_nh_dump_exceptions+0xb3/0x260 rt6_dump_route+0x53e/0x5f0 fib6_dump_node+0x6d/0xf0 fib6_walk_continue+0x290/0x2d0 fib6_dump_table+0x28d/0x360 inet6_dump_fib+0x37d/0x620 rtnl_dumpit+0x7b/0xd0 netlink_dump+0x3ae/0x7e0 ... entry_SYSCALL_64_after_hwframe+0x77/0x7f

4 locks held by dumper/549: ... #1: (rcu_read_lock){....}-{1:3}, at: inet6_dump_fib+0x88/0x620 #2: (&tb->tb6_lock){+.-.}-{3:3}, at: fib6_dump_table+0x1e9/0x360 #3: (rcu_read_lock){....}-{1:3}, at: rt6_dump_route+0x483/0x5f0

value changed: 0xffff8a7c44e05700 -> 0xffff8a7c45d60100

Reported by Kernel Concurrency Sanitizer on: CPU: 14 UID: 0 PID: 549 Comm: dumper Not tainted 7.2.0-rc7-virtme #38 PREEMPT(lazy) ...

Use hlist_for_each_entry_rcu() to safely iterate over the exception list.

Text from CVE List

Affected versions 18

  • Linuxaffected: 1e47b4837f3bdaa425727cfe09f5ae3b6c4c41a9 before dffbfb3117138e8e0e09d05f507bd36ca1f696e5CVE List
  • Linuxaffected: 1e47b4837f3bdaa425727cfe09f5ae3b6c4c41a9 before 6bd3f94ed858f2d072627546b4cdf712b0f8ea88CVE List
  • Linuxaffected: 1e47b4837f3bdaa425727cfe09f5ae3b6c4c41a9 before 9c6be625e1a7258e845d6193b3b6b084a00f8e9eCVE List
  • Linuxaffected: 1e47b4837f3bdaa425727cfe09f5ae3b6c4c41a9 before 3665abc3d2ae8a78cb67f858e848481432ec75dbCVE List
  • Linuxaffected: 1e47b4837f3bdaa425727cfe09f5ae3b6c4c41a9 before eda56ee17713f9dd834b922f7dbfa2e25fa6358cCVE List
  • Linuxaffected: 1e47b4837f3bdaa425727cfe09f5ae3b6c4c41a9 before a602cd128d17a793e12888edc8eda85821ede7e1CVE List
  • Linuxaffected: 1e47b4837f3bdaa425727cfe09f5ae3b6c4c41a9 before f6b1b15848fd91fe122dac0d19d3d666e35075b6CVE List
  • Linuxaffected: 1e47b4837f3bdaa425727cfe09f5ae3b6c4c41a9 before 47cdab0d51aaa9bd85f8e4904585bd5bd4df4488CVE List
  • Linuxaffected: 5.3CVE List
  • Linuxunaffected: all versions before 5.3CVE List
  • Linuxunaffected: 5.10.270 through 5.10.*CVE List
  • Linuxunaffected: 5.15.221 through 5.15.*CVE List
  • Linuxunaffected: 6.1.188 through 6.1.*CVE List
  • Linuxunaffected: 6.6.157 through 6.6.*CVE List
  • Linuxunaffected: 6.12.109 through 6.12.*CVE List
  • Linuxunaffected: 6.18.50 through 6.18.*CVE List
  • Linuxunaffected: 7.2.4 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 8