CVE-2026-52923 (GCVE-0-2026-52923)
Vulnerability from cvelistv5
Published
2026-06-24 07:14
Modified
2026-08-28 12:04
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ipc: limit next_id allocation to the valid ID range The checkpoint/restore sysctl path can request the next SysV IPC id through ids->next_id. ipc_idr_alloc() currently forwards that request to idr_alloc() with an open-ended upper bound. If the valid tail of the SysV IPC id space is full, the allocation can spill beyond ipc_mni. The returned SysV IPC id still uses the normal index encoding, so later lookup and removal can target the wrong slot. This leaves the real IDR entry behind and breaks the IDR state for the object. The bug is in ipc_idr_alloc() in the checkpoint/restore path. 1. ids->next_id is passed to: idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id), 0, ...) 2. The zero upper bound makes the allocation effectively open-ended. Once the valid SysV IPC tail is occupied, idr_alloc() can spill past ipc_mni and allocate an entry beyond the valid IPC id range. 3. The new object id is still encoded with the narrower SysV IPC index width: new->id = (new->seq << ipcmni_seq_shift()) + idx 4. Later removal goes through ipc_rmid(), which uses: ipcid_to_idx(ipcp->id) That truncates the real IDR index. An object actually stored at a high index can then be removed as if it lived at a low in-range index. 5. For shared memory, shm_destroy() frees the current object anyway, but the real high IDR slot is left behind as a dangling pointer. 6. A subsequent walk of /proc/sysvipc/shm reaches the stale IDR entry and dereferences freed memory. Prevent this by bounding the requested allocation to ipc_mni so the checkpoint/restore path fails once the valid range is exhausted.
References
Impacted products
Vendor Product Version
Linux Linux Version: 03f595668017f1a1fb971c02fc37140bc6e7bb1c
Version: 03f595668017f1a1fb971c02fc37140bc6e7bb1c
Version: 03f595668017f1a1fb971c02fc37140bc6e7bb1c
Version: 03f595668017f1a1fb971c02fc37140bc6e7bb1c
Version: 03f595668017f1a1fb971c02fc37140bc6e7bb1c
Version: 03f595668017f1a1fb971c02fc37140bc6e7bb1c
Version: 03f595668017f1a1fb971c02fc37140bc6e7bb1c
Version: 03f595668017f1a1fb971c02fc37140bc6e7bb1c
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.210",
                  "versionStartIncluding": "3.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.176",
                  "versionStartIncluding": "3.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.143",
                  "versionStartIncluding": "3.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.93",
                  "versionStartIncluding": "3.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.35",
                  "versionStartIncluding": "3.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.12",
                  "versionStartIncluding": "3.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "3.8",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipc: limit next_id allocation to the valid ID range\n\nThe checkpoint/restore sysctl path can request the next SysV IPC id\nthrough ids-\u003enext_id.  ipc_idr_alloc() currently forwards that request to\nidr_alloc() with an open-ended upper bound.\n\nIf the valid tail of the SysV IPC id space is full, the allocation can\nspill beyond ipc_mni.  The returned SysV IPC id still uses the normal\nindex encoding, so later lookup and removal can target the wrong slot. \nThis leaves the real IDR entry behind and breaks the IDR state for the\nobject.\n\nThe bug is in ipc_idr_alloc() in the checkpoint/restore path.\n\n1. ids-\u003enext_id is passed to:\n\n       idr_alloc(\u0026ids-\u003eipcs_idr, new, ipcid_to_idx(next_id), 0, ...)\n\n2. The zero upper bound makes the allocation effectively open-ended.\n   Once the valid SysV IPC tail is occupied, idr_alloc() can spill past\n   ipc_mni and allocate an entry beyond the valid IPC id range.\n\n3. The new object id is still encoded with the narrower SysV IPC index\n   width:\n\n       new-\u003eid = (new-\u003eseq \u003c\u003c ipcmni_seq_shift()) + idx\n\n4. Later removal goes through ipc_rmid(), which uses:\n\n       ipcid_to_idx(ipcp-\u003eid)\n\n   That truncates the real IDR index. An object actually stored at a\n   high index can then be removed as if it lived at a low in-range\n   index.\n\n5. For shared memory, shm_destroy() frees the current object anyway, but\n   the real high IDR slot is left behind as a dangling pointer.\n\n6. A subsequent walk of /proc/sysvipc/shm reaches the stale IDR entry\n   and dereferences freed memory.\n\nPrevent this by bounding the requested allocation to ipc_mni so the\ncheckpoint/restore path fails once the valid range is exhausted."
        }
      ],
      "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 vulnerable path is reached through local SysV IPC syscalls plus writes to `/proc/sys/kernel/*_next_id`, not through network or physical input.\nAC:L - The attacker controls the sysctl value, IPC allocation pattern, removal, and proc/syscall enumeration needed to trigger the stale IDR pointer; filling the valid ID tail is resource-intensive but deterministic.\nPR:L - A basic local user can reasonably reach this via unprivileged user namespaces by creating a user/IPC namespace and gaining the namespace capabilities needed for the checkpoint/restore sysctls.\nUI:N - No victim action is required after the local attacker runs the sysctl and SysV IPC operations.\nS:U - This is a standard kernel memory corruption/local privilege escalation class issue within the same kernel security authority.\nC:H - The bug leaves a freed SysV IPC object reachable through the IDR, producing a kernel use-after-free; UAFs are scored as high confidentiality impact because reclaimed kernel heap contents can be exposed or used for read primitives.\nI:H - The stale pointer/use-after-free can plausibly be exploited through heap reuse for kernel memory corruption and control-flow or object manipulation, so integrity impact is high.\nA:H - Even without full exploitation, walking `/proc/sysvipc/shm` or related enumeration can dereference freed memory and crash or hang the kernel."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:31:44.559Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3bbe2bb9111ce6967a951bfac79af142d816fae5"
        },
        {
          "url": "https://git.kernel.org/stable/c/8c58a92849175f5e2ab7bc2734b3b89afe79f6ef"
        },
        {
          "url": "https://git.kernel.org/stable/c/af24e202b543ded8a34f1d5d3db54eb916173f04"
        },
        {
          "url": "https://git.kernel.org/stable/c/157ce2c6836ce0ff19108a819f38df061345425f"
        },
        {
          "url": "https://git.kernel.org/stable/c/41058d4c3f63ab64901560a704882e0565f4e456"
        },
        {
          "url": "https://git.kernel.org/stable/c/a3cc795129e5ec0f8948653a3bf471e7d8852f5e"
        },
        {
          "url": "https://git.kernel.org/stable/c/bd4be70669af55b974860d13680348cfdf50bbed"
        },
        {
          "url": "https://git.kernel.org/stable/c/fa0b9b2b7ae3539908d69c2b9ac0d144d9bc5139"
        }
      ],
      "title": "ipc: limit next_id allocation to the valid ID range",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-52923",
    "datePublished": "2026-06-24T07:14:17.849Z",
    "dateReserved": "2026-06-09T07:44:35.367Z",
    "dateUpdated": "2026-08-28T12:04:16.286Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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