CVE-2026-89539 SUNRPC: reject duplicate CREDS_VALUE options

Q: Is CVE-2026-89539 being exploited?

There is no known exploitation of CVE-2026-89539 in the wild and no public exploit code.

Not scored Published 11 Sep 2026 Updated 21 Oct 2026

A remote attacker can cause a memory leak in the Linux kernel SUNRPC module by sending duplicate CREDS_VALUE options, leading to resource exhaustion.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-89539?

CVE-2026-89539 is a memory corruption vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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 allocation's 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.

Which versions are affected by CVE-2026-89539?

How do I fix CVE-2026-89539?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-89539 being exploited?