Bug 2400627 (CVE-2025-39926)

Summary: CVE-2025-39926 kernel: genetlink: fix genl_bind() invoking bind() after -EPERM
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-10-01 09:01:42 UTC 
In the Linux kernel, the following vulnerability has been resolved:

genetlink: fix genl_bind() invoking bind() after -EPERM

Per family bind/unbind callbacks were introduced to allow families
to track multicast group consumer presence, e.g. to start or stop
producing events depending on listeners.

However, in genl_bind() the bind() callback was invoked even if
capability checks failed and ret was set to -EPERM. This means that
callbacks could run on behalf of unauthorized callers while the
syscall still returned failure to user space.

Fix this by only invoking bind() after "if (ret) break;" check
i.e. after permission checks have succeeded.
Comment 1 Alexander B 2025-10-02 11:34:59 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025100125-CVE-2025-39926-06ea@gregkh/T