Vulnerability-Lookup

FKIE_CVE-2026-89546

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-13 07:17

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: close backchannel before destroying callback service A backchannel receive can complete a request while the NFS callback service is being torn down. xprt_complete_bc_request() removes the request from bc_pa_list, drops bc_alloc_count, marks the request in use, and then asks xprt_enqueue_bc_request() to hand it to the callback service. If teardown has already cleared xprt->bc_serv, xprt_enqueue_bc_request() currently returns without enqueueing or freeing the committed request. The xprt_get() taken on entry is leaked as well. If the producer wins the race before bc_serv is cleared, it can also enqueue onto sv_cb_list after nfs_callback_down() has stopped the callback threads, leaving the request linked to a svc_serv that is about to be freed. Close the producer side before callback threads are stopped. Add xprt_svc_shutdown_bc() to clear xprt->bc_serv under bc_pa_lock, and call it on callback shutdown and callback-start failure before stopping the service threads. Requests that lose the NULL transition in xprt_enqueue_bc_request() are released through the normal backchannel free path after balancing bc_slot_count. Finally, drain any remaining sv_cb_list requests after the callback threads have stopped and before svc_destroy() frees the service.

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3674f780f47d2906b5a0f7199b66973067bdfeca
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6debde9e3e6ae21dcca75837b4247b13ca4ea2b8

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfs/callback.c",
            "include/linux/sunrpc/bc_xprt.h",
            "net/sunrpc/backchannel_rqst.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6debde9e3e6ae21dcca75837b4247b13ca4ea2b8",
              "status": "affected",
              "version": "441244d4273a8037b265fd254dfdaca5fa736ee2",
              "versionType": "git"
            },
            {
              "lessThan": "3674f780f47d2906b5a0f7199b66973067bdfeca",
              "status": "affected",
              "version": "441244d4273a8037b265fd254dfdaca5fa736ee2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfs/callback.c",
            "include/linux/sunrpc/bc_xprt.h",
            "net/sunrpc/backchannel_rqst.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: close backchannel before destroying callback service\n\nA backchannel receive can complete a request while the NFS callback\nservice is being torn down.  xprt_complete_bc_request() removes the\nrequest from bc_pa_list, drops bc_alloc_count, marks the request in use,\nand then asks xprt_enqueue_bc_request() to hand it to the callback\nservice.\n\nIf teardown has already cleared xprt-\u003ebc_serv, xprt_enqueue_bc_request()\ncurrently returns without enqueueing or freeing the committed request.\nThe xprt_get() taken on entry is leaked as well.  If the producer wins\nthe race before bc_serv is cleared, it can also enqueue onto sv_cb_list\nafter nfs_callback_down() has stopped the callback threads, leaving the\nrequest linked to a svc_serv that is about to be freed.\n\nClose the producer side before callback threads are stopped.  Add\nxprt_svc_shutdown_bc() to clear xprt-\u003ebc_serv under bc_pa_lock, and call\nit on callback shutdown and callback-start failure before stopping the\nservice threads.  Requests that lose the NULL transition in\nxprt_enqueue_bc_request() are released through the normal backchannel\nfree path after balancing bc_slot_count.  Finally, drain any remaining\nsv_cb_list requests after the callback threads have stopped and before\nsvc_destroy() frees the service."
    }
  ],
  "id": "CVE-2026-89546",
  "lastModified": "2026-09-13T07:17:16.950",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:19:37.960",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3674f780f47d2906b5a0f7199b66973067bdfeca"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6debde9e3e6ae21dcca75837b4247b13ca4ea2b8"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-89546 (GCVE-0-2026-89546)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:44 – Updated: 2026-09-13 06:30

Title

SUNRPC: close backchannel before destroying callback service

Summary

Severity

9.8 (Critical)


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

Assigner

Linux mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/6debde9e3e6ae21dc…
https://git.kernel.org/stable/c/3674f780f47d2906b…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 441244d4273a8037b265fd254dfdaca5fa736ee2 , < 6debde9e3e6ae21dcca75837b4247b13ca4ea2b8 (git) Affected: 441244d4273a8037b265fd254dfdaca5fa736ee2 , < 3674f780f47d2906b5a0f7199b66973067bdfeca (git)
Linux	Linux	Affected: 6.19 Unaffected: 0 , < 6.19 (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfs/callback.c",
            "include/linux/sunrpc/bc_xprt.h",
            "net/sunrpc/backchannel_rqst.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "6debde9e3e6ae21dcca75837b4247b13ca4ea2b8",
              "status": "affected",
              "version": "441244d4273a8037b265fd254dfdaca5fa736ee2",
              "versionType": "git"
            },
            {
              "lessThan": "3674f780f47d2906b5a0f7199b66973067bdfeca",
              "status": "affected",
              "version": "441244d4273a8037b265fd254dfdaca5fa736ee2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfs/callback.c",
            "include/linux/sunrpc/bc_xprt.h",
            "net/sunrpc/backchannel_rqst.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: close backchannel before destroying callback service\n\nA backchannel receive can complete a request while the NFS callback\nservice is being torn down.  xprt_complete_bc_request() removes the\nrequest from bc_pa_list, drops bc_alloc_count, marks the request in use,\nand then asks xprt_enqueue_bc_request() to hand it to the callback\nservice.\n\nIf teardown has already cleared xprt-\u003ebc_serv, xprt_enqueue_bc_request()\ncurrently returns without enqueueing or freeing the committed request.\nThe xprt_get() taken on entry is leaked as well.  If the producer wins\nthe race before bc_serv is cleared, it can also enqueue onto sv_cb_list\nafter nfs_callback_down() has stopped the callback threads, leaving the\nrequest linked to a svc_serv that is about to be freed.\n\nClose the producer side before callback threads are stopped.  Add\nxprt_svc_shutdown_bc() to clear xprt-\u003ebc_serv under bc_pa_lock, and call\nit on callback shutdown and callback-start failure before stopping the\nservice threads.  Requests that lose the NULL transition in\nxprt_enqueue_bc_request() are released through the normal backchannel\nfree path after balancing bc_slot_count.  Finally, drain any remaining\nsv_cb_list requests after the callback threads have stopped and before\nsvc_destroy() frees the service."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The producer is xs_read_stream_call()/rpcrdma_bc_receive_call() handling RPC_CALL messages on the established NFSv4.1+ client TCP or RPC/RDMA transport; a malicious NFS server sends backchannel frames on that connection and reaches the bug without local access.\nAC:L - The attacker controls both sides of the race: they emit backchannel RPC_CALLs on the still-live xprt and force callback teardown via failed session setup, autofs expiry, or unmount, leaving rpc_rqst objects on sv_cb_list when svc_destroy() frees svc_serv.\nPR:N - A remote NFS peer needs no account or capability on the victim; backchannel RPC_CALLs are accepted on the connected NFSv4.1+ transport once a mount or mount attempt exists, with no local privileges at exploit time.\nUI:N - Boot-time, autofs, and Kubernetes NFSv4.1+ mounts are common; after that session exists the attacker drives backchannel traffic and callback teardown without further interactive victim action such as a manual mount.\nS:U - The use-after-free corrupts the in-kernel nfs_callback svc_serv and rpc_rqst objects on the client host and does not cross a VM, IOMMU, or other security-authority boundary.\nC:H - A raced enqueue leaves an in-use rpc_rqst linked into a freed svc_serv (sv_cb_list/sv_pools), and unlocked bc_serv readers can follow that dangling pointer, yielding a kernel-heap use-after-free read primitive.\nI:H - Use-after-free of svc_serv with queued rpc_rqst and svc_pool_wake_idle_thread on dying callback pools enables heap reuse of RPC service control structures, a standard kernel write and control-flow hijack primitive.\nA:H - svc_destroy() of a callback service that still has live backchannel requests, plus dereference of xprt-\u003ebc_serv after free, causes kernel oops or panic; the leak path also orphans rpc_rqst objects and xprt references."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:30:45.511Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/6debde9e3e6ae21dcca75837b4247b13ca4ea2b8"
        },
        {
          "url": "https://git.kernel.org/stable/c/3674f780f47d2906b5a0f7199b66973067bdfeca"
        }
      ],
      "title": "SUNRPC: close backchannel before destroying callback service",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89546",
    "datePublished": "2026-09-11T19:44:21.898Z",
    "dateReserved": "2026-09-11T19:38:34.722Z",
    "dateUpdated": "2026-09-13T06:30:45.511Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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