CVE-2026-89544

Status: UPDATED  |  Advisory ID: CVE-2026-89544

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

SUNRPC: fix gssx_dec_option_array error path bugs

Four coupled defects in the gssx XDR option-array decoder make the

error paths unsafe: a NULL deref in the caller, a refcount leak on

the decoded group_info, and a latent use-after-free that the leak

fix would otherwise expose.

gssx_dec_option_array() sets oa->count = 1 before allocating

oa->data. If that allocation fails, -ENOMEM is returned with

oa->count == 1 and oa->data == NULL. All other error paths jump

to free_oa: which frees oa->data and NULLs it but also leaves

oa->count == 1. The caller trusts the count:

gssp_accept_sec_context_upcall()

gssx_dec_accept_sec_context()

gssx_dec_option_array() /* fails, count=1 data=NULL */

data = res.options.data[0].value /* NULL deref */

Independently, free_creds: releases the partially decoded svc_cred

with a bare kfree(creds). gssx_dec_linux_creds() installs a

groups_alloc() result into creds->cr_group_info; that object is

kvmalloc-backed and refcounted, and only put_group_info() reaches

kvfree(). A plain kfree(creds) drops the wrapper and leaks the

group_info allocation.

The natural fix for the leak is to call free_svc_cred(creds) before

kfree(creds), but free_svc_cred() invokes put_group_info() on

creds->cr_group_info unconditionally when non-NULL. The existing

out_free_groups: path in gssx_dec_linux_creds() already called

groups_free() on that pointer without clearing it, so once

free_svc_cred() is wired in, the subsequent put_group_info() would

touch freed memory.

Fix all four together:

- Move the oa->count = 1 assignment below the oa->data allocation

so it is never set when oa->data is NULL.

- Reset oa->count to 0 at free_oa: so count and data stay

coherent and the caller sees an empty option array.

- Call free_svc_cred(creds) before kfree(creds) at free_creds:

so the refcounted cr_group_info is released. free_svc_cred()

either NULL-guards each field explicitly (cr_group_info has

an if() check) or delegates to a helper that is NULL-safe

itself (kfree for the string fields, gss_mech_put() which

guards with if(gm) at gss_mech_switch.c:342), so it is safe

to call on a partially decoded svc_cred where only

cr_uid/cr_gid/cr_group_info have been written and everything

else is zero from kzalloc.

- In gssx_dec_linux_creds()'s out_free_groups: path, release

cr_group_info with put_group_info() rather than groups_free()

so the teardown matches free_svc_cred()'s refcount-aware path,

and clear the pointer so a later free_svc_cred() on the same

creds does not release it a second time. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References