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CVE-2025-71097

ipv4: Fix reference count leak when using error routes with nexthop objects

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.64, and 1 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

In the Linux kernel, the following vulnerability has been resolved: ipv4: Fix reference count leak when using error routes with nexthop objects When a nexthop object is deleted, it is marked as dead and then fib_table_flush() is called to flush all the routes that are using the dead nexthop. The current logic in fib_table_flush() is to only flush error routes (e.g., blackhole) when it is called as part of network namespace dismantle (i.e., with flush_all=true). Therefore, error routes are not flushed when their nexthop object is deleted: # ip link add name dummy1 up type dummy # ip nexthop add id 1 dev dummy1 # ip route add 198.51.100.1/32 nhid 1 # ip route add blackhole 198.51.100.2/32 nhid 1 # ip nexthop del id 1 # ip route show blackhole 198.51.100.2 nhid 1 dev dummy1 As such, they keep holding a reference on the nexthop object which in turn holds a reference on the nexthop device, resulting in a reference count leak: # ip link del dev dummy1 [ 70.516258] unregister_netdevice: waiting for dummy1 to become free. Usage count = 2 Fix by flushing error routes when their nexthop is marked as dead. IPv6 does not suffer from this problem.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux Linux

    From 493ced1ac47c48bb86d9d4e8e87df8592be85a0e · fixed in 5de7ad7e18356e39e8fbf7edd185a5faaf4f385a; From 493ced1ac47c48bb86d9d4e8e87df8592be85a0e · fixed in 33ff5c207c873215e54e6176624ed57423cb7dea; From 493ced1ac47c48bb86d9d4e8e87df8592be85a0e · fixed in 30386e090c49e803c0616a7147e43409c32a2b0e; From 493ced1ac47c48bb86d9d4e8e87df8592be85a0e · fixed in 5979338c83012110ccd45cae6517591770bfe536; From 493ced1ac47c48bb86d9d4e8e87df8592be85a0e · fixed in ee4183501ea556dca31f5ffd8690aa9fd25b609f; From 493ced1ac47c48bb86d9d4e8e87df8592be85a0e · fixed in e3fc381320d04e4a74311e576a86cac49a16fc43; From 493ced1ac47c48bb86d9d4e8e87df8592be85a0e · fixed in ac782f4e3bfcde145b8a7f8af31d9422d94d172a

  • Linux Linux

    5.3

  • KernelLinux

    From 5.3.0 · fixed in 5.10.248; From 5.11.0 · fixed in 5.15.198; From 5.16.0 · fixed in 6.1.160; From 6.2.0 · fixed in 6.6.120; From 6.7.0 · fixed in 6.12.64; From 6.13.0 · fixed in 6.18.4

References 7

git.kernel.org