EUVD-2026-76451
GHSA-gwh2-5395-p8p6
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Race condition exploitation requires precise timing (AC:H); local proc-file write requires minimal privilege (PR:L); no scope change as impact is confined to the kernel.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
6DescriptionCVE.org
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.
AnalysisAI
Linux kernel SUNRPC subsystem exposes a race condition between proc entry publication and mutex initialization in the GSS proxy path, allowing a local attacker with write access to /proc/net/rpc/use-gss-proxy to exploit an uninitialized mutex during the narrow window when auth_rpcgss loads. On a production kernel without debug options, two concurrent writers racing through set_gssp_clnt() can shut down an RPC client structure while it is still in active use, resulting in a resource leak and potential use-after-free with full kernel memory integrity and availability impact. …
Unlock full vulnerability intelligence
- Risk assessment & exploitation conditions
- Attack chain visualization
- Remediation with exact patch versions
- Threat intelligence from 22 sources
- Personal watchlist & email alerts
Free forever · No credit card required
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires: (1) local access to a Linux system with the auth_rpcgss module loadable or being loaded (e.g., triggered by an NFS Kerberos mount); (2) write access to /proc/net/rpc/use-gss-proxy, which is available to privileged local users or processes with appropriate DAC/MAC permissions; (3) ability to time a write to the proc file within the narrow window between proc_create_data() returning and mutex_init() completing in init_gssp_clnt() - a window that spans only two kernel instructions but widens during auth_rpcgss module load across all live network namespaces. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD CVSS 3.1 vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H scores 7.8, but AC:L understates real exploitability - this is a race condition requiring a write to land in a narrow window between two kernel statements, strongly suggesting AC:H is the more accurate metric. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply the vendor-released fix by upgrading to Linux 6.12.109, 6.18.50, 7.2.4, or 7.3-rc1 as appropriate for your stable branch. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: obtain the list of vulnerable kernel versions from your Linux distribution's security advisory and identify all affected systems in your infrastructure. …
Sign in for detailed remediation steps and compensating controls.
Threat intelligence, references, and detailed analysis are available after sign-in.
Share
External POC / Exploit Code
Leaving vuln.today