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CVE-2024-26870 (GCVE-0-2024-26870)

Vulnerability from cvelistv5 – Published: 2024-04-17 10:27 – Updated: 2026-08-05 11:28
VLAI
Title
NFSv4.2: fix nfs4_listxattr kernel BUG at mm/usercopy.c:102
Summary
In the Linux kernel, the following vulnerability has been resolved: NFSv4.2: fix nfs4_listxattr kernel BUG at mm/usercopy.c:102 A call to listxattr() with a buffer size = 0 returns the actual size of the buffer needed for a subsequent call. When size > 0, nfs4_listxattr() does not return an error because either generic_listxattr() or nfs4_listxattr_nfs4_label() consumes exactly all the bytes then size is 0 when calling nfs4_listxattr_nfs4_user() which then triggers the following kernel BUG: [ 99.403778] kernel BUG at mm/usercopy.c:102! [ 99.404063] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP [ 99.408463] CPU: 0 PID: 3310 Comm: python3 Not tainted 6.6.0-61.fc40.aarch64 #1 [ 99.415827] Call trace: [ 99.415985] usercopy_abort+0x70/0xa0 [ 99.416227] __check_heap_object+0x134/0x158 [ 99.416505] check_heap_object+0x150/0x188 [ 99.416696] __check_object_size.part.0+0x78/0x168 [ 99.416886] __check_object_size+0x28/0x40 [ 99.417078] listxattr+0x8c/0x120 [ 99.417252] path_listxattr+0x78/0xe0 [ 99.417476] __arm64_sys_listxattr+0x28/0x40 [ 99.417723] invoke_syscall+0x78/0x100 [ 99.417929] el0_svc_common.constprop.0+0x48/0xf0 [ 99.418186] do_el0_svc+0x24/0x38 [ 99.418376] el0_svc+0x3c/0x110 [ 99.418554] el0t_64_sync_handler+0x120/0x130 [ 99.418788] el0t_64_sync+0x194/0x198 [ 99.418994] Code: aa0003e3 d000a3e0 91310000 97f49bdb (d4210000) Issue is reproduced when generic_listxattr() returns 'system.nfs4_acl', thus calling lisxattr() with size = 16 will trigger the bug. Add check on nfs4_listxattr() to return ERANGE error when it is called with size > 0 and the return value is greater than size.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-05-28 19:56 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 012a211abd5db098094ce429de5f046368391e68 , < 4403438eaca6e91f02d272211c4d6b045092396b (git)
Affected: 012a211abd5db098094ce429de5f046368391e68 , < 9d52865ff28245fc2134da9f99baff603a24407a (git)
Affected: 012a211abd5db098094ce429de5f046368391e68 , < 06e828b3f1b206de08ef520fc46a40b22e1869cb (git)
Affected: 012a211abd5db098094ce429de5f046368391e68 , < 79cdcc765969d23f4e3d6ea115660c3333498768 (git)
Affected: 012a211abd5db098094ce429de5f046368391e68 , < 80365c9f96015bbf048fdd6c8705d3f8770132bf (git)
Affected: 012a211abd5db098094ce429de5f046368391e68 , < 23bfecb4d852751d5e403557dd500bb563313baf (git)
Affected: 012a211abd5db098094ce429de5f046368391e68 , < 251a658bbfceafb4d58c76b77682c8bf7bcfad65 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.9
Unaffected: 0 , < 5.9 (semver)
Unaffected: 5.10.214 , ≤ 5.10.* (semver)
Unaffected: 5.15.153 , ≤ 5.15.* (semver)
Unaffected: 6.1.83 , ≤ 6.1.* (semver)
Unaffected: 6.6.23 , ≤ 6.6.* (semver)
Unaffected: 6.7.11 , ≤ 6.7.* (semver)
Unaffected: 6.8.2 , ≤ 6.8.* (semver)
Unaffected: 6.9 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem Affected: 0 , < * (custom)
guessed Create a notification for this product.
Show details on NVD website
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              "value": "AV:L - The vulnerability is triggered by a local `listxattr(2)`/`llistxattr(2)`/`flistxattr(2)` syscall on a file residing on an NFSv4 mount; no network peer can initiate it on its own. Although the overflow content is supplied by the NFS server over the wire, a local syscall is required to reach the code, so the attack vector is Local.\nAC:L - Triggering is fully deterministic \u2014 the attacker probes with `size = 0`, then calls `listxattr()` with a size exactly equal to the generic handler list (16 bytes for `\"system.nfs4_acl\\0\"`), with no race to win and no memory-layout condition outside their control. The required config (CONFIG_NFS_V4_2, CONFIG_NFS_V4_SECURITY_LABEL, CONFIG_HARDENED_USERCOPY) is enabled by default on mainstream distributions, as demonstrated by the reporter reproducing on a stock Fedora 40 kernel.\nPR:L - Any unprivileged local user with ordinary access to a file on an existing NFSv4.2 mount can call `listxattr()` and set the `user.*` xattrs that become the overflow payload; no capabilities are needed. NFS-mounted home directories on shared/multi-user hosts make this a standard unprivileged-user reach.\nUI:N - The attacker performs every step \u2014 setting the xattrs and issuing the sized `listxattr()` call \u2014 with no action by any other user. The pre-existing NFS mount is an environmental property of the deployment, not an interaction the attacker must induce.\nS:U - The over-read, the leaked data, and the heap overflow all occur within the kernel\u0027s own memory and are delivered to the attacker\u0027s own process. No VM, IOMMU, or other security-authority boundary is crossed.\nC:H - When hardened usercopy is not enforcing, `copy_to_user()` transfers up to XATTR_LIST_MAX (64 KB) of kernel heap memory past a 16-byte kmalloc object directly into the attacker\u0027s buffer, with the over-read length controlled by how many `user.*` xattrs the attacker attaches to the file. This is a large, attacker-sized disclosure of adjacent slab contents including potential pointers and other tasks\u0027 data.\nI:H - The `size_t` underflow hands `nfs4_listxattr_nfs4_user()` a past-the-end pointer with an effectively unbounded length, and `decode_listxattrs()` then memcpy()s `user.\u003cattacker-chosen-name\u003e\\0` records past the end of a kmalloc-16 object in a loop until EOF. This is a heap buffer overflow with attacker-controlled content, length, and destination slab, which is a strong primitive for adjacent-object corruption and control-flow hijacking.\nA:H - The reported and reproducible outcome is `usercopy_abort()` calling `BUG()` at mm/usercopy.c:102 \u2014 a kernel oops that is a full panic on systems with `panic_on_oops` (common on embedded, automotive, and hardened deployments), repeatable at will by any local user. The heap overflow path additionally corrupts slab metadata and adjacent objects, causing further crashes."
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSv4.2: fix nfs4_listxattr kernel BUG at mm/usercopy.c:102\n\nA call to listxattr() with a buffer size = 0 returns the actual\nsize of the buffer needed for a subsequent call. When size \u003e 0,\nnfs4_listxattr() does not return an error because either\ngeneric_listxattr() or nfs4_listxattr_nfs4_label() consumes\nexactly all the bytes then size is 0 when calling\nnfs4_listxattr_nfs4_user() which then triggers the following\nkernel BUG:\n\n  [   99.403778] kernel BUG at mm/usercopy.c:102!\n  [   99.404063] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP\n  [   99.408463] CPU: 0 PID: 3310 Comm: python3 Not tainted 6.6.0-61.fc40.aarch64 #1\n  [   99.415827] Call trace:\n  [   99.415985]  usercopy_abort+0x70/0xa0\n  [   99.416227]  __check_heap_object+0x134/0x158\n  [   99.416505]  check_heap_object+0x150/0x188\n  [   99.416696]  __check_object_size.part.0+0x78/0x168\n  [   99.416886]  __check_object_size+0x28/0x40\n  [   99.417078]  listxattr+0x8c/0x120\n  [   99.417252]  path_listxattr+0x78/0xe0\n  [   99.417476]  __arm64_sys_listxattr+0x28/0x40\n  [   99.417723]  invoke_syscall+0x78/0x100\n  [   99.417929]  el0_svc_common.constprop.0+0x48/0xf0\n  [   99.418186]  do_el0_svc+0x24/0x38\n  [   99.418376]  el0_svc+0x3c/0x110\n  [   99.418554]  el0t_64_sync_handler+0x120/0x130\n  [   99.418788]  el0t_64_sync+0x194/0x198\n  [   99.418994] Code: aa0003e3 d000a3e0 91310000 97f49bdb (d4210000)\n\nIssue is reproduced when generic_listxattr() returns \u0027system.nfs4_acl\u0027,\nthus calling lisxattr() with size = 16 will trigger the bug.\n\nAdd check on nfs4_listxattr() to return ERANGE error when it is\ncalled with size \u003e 0 and the return value is greater than size."
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            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: NFSv4.2: corrige el ERROR del kernel nfs4_listxattr en mm/usercopy.c:102 Una llamada a listxattr() con un tama\u00f1o de b\u00fafer = 0 devuelve el tama\u00f1o real del b\u00fafer necesario para un convocatoria posterior. Cuando el tama\u00f1o \u0026gt; 0, nfs4_listxattr() no devuelve un error porque generic_listxattr() o nfs4_listxattr_nfs4_label() consume exactamente todos los bytes, entonces el tama\u00f1o es 0 al llamar a nfs4_listxattr_nfs4_user(), lo que luego activa el siguiente ERROR del kernel: [99.403778] ERROR del kernel en mm/usercopy.c:102! [99.404063] Error interno: Ups - ERROR: 00000000f2000800 [#1] SMP [99.408463] CPU: 0 PID: 3310 Comm: python3 No contaminado 6.6.0-61.fc40.aarch64 #1 [ 99.415827] Seguimiento de llamadas: [ 99.41 5985] usercopy_abort+0x70/0xa0 [ 99.416227] __check_heap_object+0x134/0x158 [ 99.416505] check_heap_object+0x150/0x188 [ 99.416696] __check_object_size.part.0+0x78/0x168 [ 99.416886 ] __check_object_size+0x28/0x40 [ 99.417078] listxattr+0x8c/0x120 [ 99.417252] path_listxattr+0x78/0xe0 [ 99.417476] __arm64_sys_listxattr+0x28/0x40 [ 99.417723] invoke_syscall+0x78/0x100 [ 99.417929] 48/0xf0 [ 99.418186] do_el0_svc+0x24/0x38 [ 99.418376] el0_svc+0x3c/ 0x110 [ 99.418554] el0t_64_sync_handler+0x120/0x130 [ 99.418788] el0t_64_sync+0x194/0x198 [ 99.418994] C\u00f3digo: aa0003e3 d000a3e0 91310000 97f49bdb (d42 10000) El problema se reproduce cuando generic_listxattr() devuelve \u0027system.nfs4_acl\u0027, llamando as\u00ed a lisxattr() con tama\u00f1o = 16 activar\u00e1 el error. Agregue verificaci\u00f3n en nfs4_listxattr() para devolver el error ERANGE cuando se llama con un tama\u00f1o \u0026gt; 0 y el valor de retorno es mayor que el tama\u00f1o."
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                  "version": "6.1.83",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.23",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.7.*",
                  "status": "unaffected",
                  "version": "6.7.11",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.8.*",
                  "status": "unaffected",
                  "version": "6.8.2",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "6.9",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.10.214",
                      "versionStartIncluding": "5.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.15.153",
                      "versionStartIncluding": "5.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.1.83",
                      "versionStartIncluding": "5.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.6.23",
                      "versionStartIncluding": "5.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.7.11",
                      "versionStartIncluding": "5.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.8.2",
                      "versionStartIncluding": "5.9",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.9",
                      "versionStartIncluding": "5.9",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSv4.2: fix nfs4_listxattr kernel BUG at mm/usercopy.c:102\n\nA call to listxattr() with a buffer size = 0 returns the actual\nsize of the buffer needed for a subsequent call. When size \u003e 0,\nnfs4_listxattr() does not return an error because either\ngeneric_listxattr() or nfs4_listxattr_nfs4_label() consumes\nexactly all the bytes then size is 0 when calling\nnfs4_listxattr_nfs4_user() which then triggers the following\nkernel BUG:\n\n  [   99.403778] kernel BUG at mm/usercopy.c:102!\n  [   99.404063] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP\n  [   99.408463] CPU: 0 PID: 3310 Comm: python3 Not tainted 6.6.0-61.fc40.aarch64 #1\n  [   99.415827] Call trace:\n  [   99.415985]  usercopy_abort+0x70/0xa0\n  [   99.416227]  __check_heap_object+0x134/0x158\n  [   99.416505]  check_heap_object+0x150/0x188\n  [   99.416696]  __check_object_size.part.0+0x78/0x168\n  [   99.416886]  __check_object_size+0x28/0x40\n  [   99.417078]  listxattr+0x8c/0x120\n  [   99.417252]  path_listxattr+0x78/0xe0\n  [   99.417476]  __arm64_sys_listxattr+0x28/0x40\n  [   99.417723]  invoke_syscall+0x78/0x100\n  [   99.417929]  el0_svc_common.constprop.0+0x48/0xf0\n  [   99.418186]  do_el0_svc+0x24/0x38\n  [   99.418376]  el0_svc+0x3c/0x110\n  [   99.418554]  el0t_64_sync_handler+0x120/0x130\n  [   99.418788]  el0t_64_sync+0x194/0x198\n  [   99.418994] Code: aa0003e3 d000a3e0 91310000 97f49bdb (d4210000)\n\nIssue is reproduced when generic_listxattr() returns \u0027system.nfs4_acl\u0027,\nthus calling lisxattr() with size = 16 will trigger the bug.\n\nAdd check on nfs4_listxattr() to return ERANGE error when it is\ncalled with size \u003e 0 and the return value is greater than size."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - The vulnerability is triggered by a local `listxattr(2)`/`llistxattr(2)`/`flistxattr(2)` syscall on a file residing on an NFSv4 mount; no network peer can initiate it on its own. Although the overflow content is supplied by the NFS server over the wire, a local syscall is required to reach the code, so the attack vector is Local.\nAC:L - Triggering is fully deterministic \u2014 the attacker probes with `size = 0`, then calls `listxattr()` with a size exactly equal to the generic handler list (16 bytes for `\"system.nfs4_acl\\0\"`), with no race to win and no memory-layout condition outside their control. The required config (CONFIG_NFS_V4_2, CONFIG_NFS_V4_SECURITY_LABEL, CONFIG_HARDENED_USERCOPY) is enabled by default on mainstream distributions, as demonstrated by the reporter reproducing on a stock Fedora 40 kernel.\nPR:L - Any unprivileged local user with ordinary access to a file on an existing NFSv4.2 mount can call `listxattr()` and set the `user.*` xattrs that become the overflow payload; no capabilities are needed. NFS-mounted home directories on shared/multi-user hosts make this a standard unprivileged-user reach.\nUI:N - The attacker performs every step \u2014 setting the xattrs and issuing the sized `listxattr()` call \u2014 with no action by any other user. The pre-existing NFS mount is an environmental property of the deployment, not an interaction the attacker must induce.\nS:U - The over-read, the leaked data, and the heap overflow all occur within the kernel\u0027s own memory and are delivered to the attacker\u0027s own process. No VM, IOMMU, or other security-authority boundary is crossed.\nC:H - When hardened usercopy is not enforcing, `copy_to_user()` transfers up to XATTR_LIST_MAX (64 KB) of kernel heap memory past a 16-byte kmalloc object directly into the attacker\u0027s buffer, with the over-read length controlled by how many `user.*` xattrs the attacker attaches to the file. This is a large, attacker-sized disclosure of adjacent slab contents including potential pointers and other tasks\u0027 data.\nI:H - The `size_t` underflow hands `nfs4_listxattr_nfs4_user()` a past-the-end pointer with an effectively unbounded length, and `decode_listxattrs()` then memcpy()s `user.\u003cattacker-chosen-name\u003e\\0` records past the end of a kmalloc-16 object in a loop until EOF. This is a heap buffer overflow with attacker-controlled content, length, and destination slab, which is a strong primitive for adjacent-object corruption and control-flow hijacking.\nA:H - The reported and reproducible outcome is `usercopy_abort()` calling `BUG()` at mm/usercopy.c:102 \u2014 a kernel oops that is a full panic on systems with `panic_on_oops` (common on embedded, automotive, and hardened deployments), repeatable at will by any local user. The heap overflow path additionally corrupts slab metadata and adjacent objects, causing further crashes."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-05T11:28:01.958Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/4403438eaca6e91f02d272211c4d6b045092396b"
            },
            {
              "url": "https://git.kernel.org/stable/c/9d52865ff28245fc2134da9f99baff603a24407a"
            },
            {
              "url": "https://git.kernel.org/stable/c/06e828b3f1b206de08ef520fc46a40b22e1869cb"
            },
            {
              "url": "https://git.kernel.org/stable/c/79cdcc765969d23f4e3d6ea115660c3333498768"
            },
            {
              "url": "https://git.kernel.org/stable/c/80365c9f96015bbf048fdd6c8705d3f8770132bf"
            },
            {
              "url": "https://git.kernel.org/stable/c/23bfecb4d852751d5e403557dd500bb563313baf"
            },
            {
              "url": "https://git.kernel.org/stable/c/251a658bbfceafb4d58c76b77682c8bf7bcfad65"
            }
          ],
          "title": "NFSv4.2: fix nfs4_listxattr kernel BUG at mm/usercopy.c:102",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2024-26870",
        "datePublished": "2024-04-17T10:27:30.756Z",
        "dateReserved": "2024-02-19T14:20:24.184Z",
        "dateUpdated": "2026-08-05T11:28:01.958Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.