CVE-2026-97597ipv6: flowlabel: cap duplicate leases per socket

Official description

In the Linux kernel, the following vulnerability has been resolved: ipv6: flowlabel: cap duplicate leases per socket ipv6_flowlabel_get() allocates an ipv6_fl_socklist entry for every successful GET. The recheck path for a compatible existing flowlabel links another lease without applying any lease admission check. Repeated GET requests for one shareable label can therefore grow a socket's lease list without bound. Reject a new unprivileged lease once the socket already holds FL_MAX_PER_SOCK leases. Check this on the shared recheck path so reuse of a globally interned label, including the fl_intern() collision path, is covered as well. New-label admission remains under the existing mem_check() policy. Use capable(CAP_NET_ADMIN) rather than ns_capable(), matching mem_check(). An unprivileged user must not bypass the cap by creating a user namespace and a netns where they have CAP_NET_ADMIN, which would still consume host memory. Check the capability only when the socket reaches the limit, so successful unprivileged GET requests below the cap do not generate a capability audit. Do the admission check before updating linger and expires so a rejected GET does not refresh the shared label, matching the existing socket-list allocation failure path.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/42abef116bb2265eeccae55a0dc91a9f1546f74c
• https://git.kernel.org/stable/c/0159f716d8adbe85951cdf008d0afe27d874eaa6
• https://git.kernel.org/stable/c/6d917992c22b6029fc2dc1bd464b7f6709357161
• https://git.kernel.org/stable/c/2f1a6dd5c80ceb902f50449efe899f29cd7918e3
• https://git.kernel.org/stable/c/467467bf4209f9f8add0c648bae763f92a0224c3
• https://git.kernel.org/stable/c/8d6cd188508513503805c156165de38e4e4a8615