Linux Kernel IPv4 FIB Dump Null Deref due to Nexthop Group Shrink
CVE-2026-99073 Published on October 23, 2026

ipv4: stop exception dump when nexthop group shrinks
In the Linux kernel, the following vulnerability has been resolved: ipv4: stop exception dump when nexthop group shrinks Commit 4ce5dc9316de ("inet: switch inet_dump_fib() to RCU protection") allowed IPv4 FIB dumps to run concurrently with nexthop replacement. fib_dump_info_fnhe() uses fib_info_num_path() as the loop bound, then fib_info_nhc() independently reloads nh->nh_grp. If RTM_NEWNEXTHOP replaces a group with fewer paths between those loads, fib_info_nhc() returns NULL and the dump dereferences it through nhc_flags. Stop the walk when the indexed path is absent. Nexthop groups are dense, so the current snapshot has no later path.

NVD

Products Associated with CVE-2026-99073

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Linux Kernel

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Affected Versions

• Version 4ce5dc9316de50e0da84beafe55d1344f829cece and below f91e472821e32f58b03eb631e20a67157e2b928b is affected.
• Version 4ce5dc9316de50e0da84beafe55d1344f829cece and below 21cba134c30c17ae55f468b5809336437df5d7e6 is affected.
• Version 4ce5dc9316de50e0da84beafe55d1344f829cece and below b9a30bb7b831e8c5a47fadbdf1760918aaf009cc is affected.
• Version 4ce5dc9316de50e0da84beafe55d1344f829cece and below 4f4afc07dcb2edd4f9afa36595373f8cdb9b58c2 is affected.

• Version 6.9 is affected.
• Before 6.9 is unaffected.
• Version 6.12.113, <= 6.12.* is unaffected.
• Version 6.18.57, <= 6.18.* is unaffected.
• Version 7.2.11, <= 7.2.* is unaffected.
• Version 7.3, <= * is unaffected.

Exploit Probability