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CVE Record

CVE-2024-56779: nfsd: fix nfs4_openowner leak when concurrent nfsd4_open occur

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix nfs4_openowner leak when concurrent nfsd4_open occur The action force umount(umount -f) will attempt to kill all rpc_task even umount operation may ultimately fail if some files remain open. Consequently, if an action attempts to open a file, it can potentially send two rpc_task to nfs server. NFS CLIENT thread1 thread2 open("file") ... nfs4_do_open _nfs4_do_open _nfs4_open_and_get_state _nfs4_proc_open nfs4_run_open_task /* rpc_task1 */ rpc_run_task rpc_wait_for_completion_task umount -f nfs_umount_begin rpc_killall_tasks rpc_signal_task rpc_task1 been wakeup and return -512 _nfs4_do_open // while loop ... nfs4_run_open_task /* rpc_task2 */ rpc_run_task rpc_wait_for_completion_task While processing an open request, nfsd will first attempt to find or allocate an nfs4_openowner. If it finds an nfs4_openowner that is not marked as NFS4_OO_CONFIRMED, this nfs4_openowner will released. Since two rpc_task can attempt to open the same file simultaneously from the client to server, and because two instances of nfsd can run concurrently, this situation can lead to lots of memory leak. Additionally, when we echo 0 to /proc/fs/nfsd/threads, warning will be triggered. NFS SERVER nfsd1 nfsd2 echo 0 > /proc/fs/nfsd/threads nfsd4_open nfsd4_process_open1 find_or_alloc_open_stateowner // alloc oo1, stateid1 nfsd4_open nfsd4_process_open1 find_or_alloc_open_stateowner // find oo1, without NFS4_OO_CONFIRMED release_openowner unhash_openowner_locked list_del_init(&oo->oo_perclient) // cannot find this oo // from client, LEAK!!! alloc_stateowner // alloc oo2 nfsd4_process_open2 init_open_stateid // associate oo1 // with stateid1, stateid1 LEAK!!! nfs4_get_vfs_file // alloc nfsd_file1 and nfsd_file_mark1 // all LEAK!!! nfsd4_process_open2 ... write_threads ... nfsd_destroy_serv nfsd_shutdown_net nfs4_state_shutdown_net nfs4_state_destroy_net destroy_client __destroy_client // won't find oo1!!! nfsd_shutdown_generic nfsd_file_cache_shutdown kmem_cache_destroy for nfsd_file_slab and nfsd_file_mark_slab // bark since nfsd_file1 // and nfsd_file_mark1 // still alive ======================================================================= BUG nfsd_file (Not tainted): Objects remaining in nfsd_file on __kmem_cache_shutdown() ----------------------------------------------------------------------- Slab 0xffd4000004438a80 objects=34 used=1 fp=0xff11000110e2ad28 flags=0x17ffffc0000240(workingset|head|node=0|zone=2|lastcpupid=0x1fffff) CPU: 4 UID: 0 PID: 757 Comm: sh Not tainted 6.12.0-rc6+ #19 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Call Trace: <TASK> dum ---truncated---

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A Linux NFS server can leak kernel memory when concurrent file-open requests race during a forced client unmount. Repetition may consume resources and disrupt service. The supplied record rates it critical, although its technical description demonstrates memory leakage and shutdown warnings, not confirmed data theft or modification.

Executive priority

Treat remediation as urgent for exposed or business-critical NFS servers because repeated leakage could impair availability. Prioritize by NFS service exposure and operational importance. Systems not serving NFS are unlikely to encounter the described path. Do not infer confirmed confidentiality or integrity compromise solely from the supplied 9.8 score.

Technical view

CVE-2024-56779 is a CWE-401 resource leak in Linux nfsd. Concurrent NFSv4 OPEN processing can release an unconfirmed open owner while another request still associates state and file objects with it. Those objects become unreachable during cleanup, causing leaks and slab-cache warnings. Stable-kernel commits are supplied as fixes.

Likely exposure

Exposure is limited to systems running affected Linux kernels as NFS servers, particularly where concurrent NFSv4 opens and forced client unmounts occur. The bundled version data is insufficiently structured for reliable branch-by-branch conclusions; confirm applicability through the kernel or distribution advisory for each deployed build.

Exploitation context

The bundle does not establish active exploitation, and the CVE is not identified as KEV. It describes a concurrency-triggered server-side memory leak involving client opens and forced unmount behavior. Network reachability may enable triggering, but attacker control, reproducibility, and impact beyond resource exhaustion are not demonstrated here.

Researcher notes

The record’s CVSS 9.8 vector claims high confidentiality, integrity, and availability impact, while the supplied technical evidence directly supports a memory leak and cleanup warnings. No public exploitation evidence is included. Researchers should distinguish the demonstrated availability risk from unsubstantiated data compromise and verify exact affected ranges against stable-tree or distribution metadata.

Mitigation direction

  • Install a distribution kernel containing the applicable referenced stable-kernel fix.
  • Prioritize internet-accessible or broadly reachable NFS servers for remediation.
  • Restrict NFS access to required, trusted clients using existing network controls.
  • Minimize forced unmounts during active NFS operations until patched, where operationally feasible.
  • Check vendor guidance before applying branch-specific kernel changes.

Validation and detection

  • Inventory Linux systems currently providing NFS exports and record their running kernels.
  • Map each kernel build to its distribution advisory or applicable stable fix commit.
  • Confirm the corrected kernel is active after installation and reboot.
  • Review kernel logs for nfsd shutdown warnings or remaining nfsd_file objects.
  • Regression-test concurrent NFSv4 opens and service shutdown in an isolated environment.
Prepared
Confidence
high
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cve · low confidence lookup

CVE-2024-56779 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
3Timeline events
2ADP providers
10Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Linux
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

9.8Critical
CVSS 3.1 vector shape for CVE-2024-56779Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux3234975f477f746c22d076ea178a79ea104b2ca7, 3234975f477f746c22d076ea178a79ea104b2ca7, 3234975f477f746c22d076ea178a79ea104b2ca7, 3234975f477f746c22d076ea178a79ea104b2ca7, 3234975f477f746c22d076ea178a79ea104b2ca7, 3234975f477f746c22d076ea178a79ea104b2ca7, 3234975f477f746c22d076ea178a79ea104b2ca7unaffected
LinuxLinux3.17, 0, 5.4.287, 5.10.231, 5.15.174, 6.1.120, 6.6.64, 6.12.4, 6.13affected
Weakness

CWE details

CWE-401

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-401 · source CWE mapping

Missing Release of Memory after Effective Lifetime

Missing Release of Memory after Effective Lifetime represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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