CVE-2026-89539

In the Linux kernel, the following vulnerability has been resolved:

SUNRPC: reject duplicate CREDS_VALUE options

gssx_dec_option_array() walks the wire-supplied option array and, for every entry whose name matches CREDS_VALUE, calls gssx_dec_linux_creds() on the same struct svc_cred. That helper unconditionally installs a fresh groups_alloc() result into creds->cr_group_info without releasing whatever pointer was already there:

for (i = 0; i < count; i++) {
    ... decode name ...
    if (length == sizeof(CREDS_VALUE) &&
        memcmp(p, CREDS_VALUE, sizeof(CREDS_VALUE)) == 0) {
        err = gssx_dec_linux_creds(xdr, creds);
        ...
    }
}

A reply that carries two CREDS_VALUE entries therefore overwrites cr_group_info on the second iteration and orphans the group_info allocated by the first call. The earlier free_creds path only releases the last cr_group_info via free_svc_cred(), so the first allocations refcount stays at one and its kvmalloc-backed storage is leaked. No in-tree caller of gssp_accept_sec_context_upcall() expects more than one CREDS_VALUE per reply.

Fix by tracking whether a CREDS_VALUE option has already been decoded and returning -EINVAL on any subsequent match, so the free_creds path releases the single group_info that was installed.

Affected Software

References

• https://git.kernel.org/stable/c/2e4ce62385c1b8a887c5370af058ac7b52a8eaf9
• https://git.kernel.org/stable/c/7a1d0501cbb962beba23377035d667bf3c1726ee
• https://git.kernel.org/stable/c/9d94f046b23de0f77849ea69133063c949297e30
• https://git.kernel.org/stable/c/f615b884310bf82d0014e3b5a92eb9aa88146685