EUVD-2026-76456
GHSA-43p7-fx92-rp4x
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Race condition during thread exit warrants AC:H; PR:L reflects local nfsd interaction required; no scope change from kernel UAF.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
6DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
sunrpc: defer rq_argp and rq_resp free until after RCU grace period
svc_rqst_free() frees rqstp->rq_argp and rqstp->rq_resp synchronously via kfree(), but defers the rqstp struct free via kfree_rcu(). After svc_exit_thread() calls list_del_rcu() and svc_rqst_free(), there is a window where RCU readers that started before list_del_rcu() can still traverse the thread list and find the rqstp. These readers (e.g. nfsd_nl_rpc_status_get_dumpit()) dereference rqstp->rq_argp, which has already been freed - a use-after-free.
Fix this by moving the kfree of rq_argp and rq_resp into an explicit call_rcu() callback alongside the struct free. Resources not accessed by RCU readers (bvec, buffer pages, scratch folio, auth_data) remain synchronously freed.
AnalysisAI
Use-after-free in the Linux kernel's SUNRPC server thread cleanup allows local attackers to trigger kernel heap reads of freed memory when RCU readers race with svc_exit_thread(). The root cause is an asymmetry in svc_rqst_free(): the rqstp struct is correctly deferred via kfree_rcu(), but rq_argp and rq_resp are freed synchronously before the RCU grace period expires - leaving a window where readers like nfsd_nl_rpc_status_get_dumpit() can dereference the freed pointers. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires: (1) Linux kernel between commit 812443865c5f (~3.19) and the fix commits, (2) an active NFS server (nfsd running - non-default for most workstations, standard for NFS file servers), (3) concurrent RCU traversal of the SUNRPC thread list via a reader such as nfsd_nl_rpc_status_get_dumpit() racing a service thread exit via svc_exit_thread(). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The provided CVSS vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, 7.8) correctly identifies the local attack vector and low-privilege requirement but assigns AC:L, which appears optimistic for a race condition that depends on precise timing between thread exit and concurrent RCU traversal - AC:H is more defensible. … 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 | Update the Linux kernel to 7.2.4, 6.18.50, or 7.3-rc1, or apply the stable backport commits (e0c5693d3f9a, c479bde671cb, 08bc49e05412) available at https://git.kernel.org/stable/c/. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Linux systems running NFS servers (verify via systemctl status nfsd) and inventory the kernel versions deployed across your NFS infrastructure against your vendor's affected versions. …
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