CVE-2026-100071: net: hsr: free learned nodes on device setup failure

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-25 · updated 2026-10-21

Description

In the Linux kernel, the following vulnerability has been resolved: net: hsr: free learned nodes on device setup failure hsr_dev_finalize() can fail after a lower-device RX handler has already been registered (slave A is added before the failable slave B and interlink adds). RX handlers run in softirq regardless of the master's state, so frames received in that window can learn dynamic nodes into node_db, and the error unwind never releases them. Free both owned dynamic databases in the unwind, mirroring hsr_dellink(). proxy_node_db is provably empty on every current error exit (only interlink RX feeds it, and the interlink add is the last failable step) and is freed for symmetry. The order is safe: hsr_del_port() unregisters each RX handler with synchronize_net() before hsr_del_nodes() runs, which removes remaining entries with list_del_rcu() and defers their release with call_rcu() for readers already under RCU.

Affected products

Linux kernel: from 3.17 before 6.1.188; from 6.2 before 6.6.157; from 6.7 before 6.12.110; from 6.13 before 6.18.52; from 6.19 before 7.2.6 — fixed in 6.1.188, 6.12.110, 6.18.52, 6.6.157, 7.2.6

How to fix

Upgrade to a fixed version: Linux kernel 6.1.188, 6.12.110, 6.18.52, 6.6.157. Check the vendor advisory for mitigations.

References

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