CVE-2026-80955 (GCVE-0-2026-80955)
Vulnerability from cvelistv5
Published
2026-09-11 19:42
Modified
2026-10-19 08:45
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: dm-pcache: fix use-after-free and invalid seg operations in kset_replay() In kset_replay, when key->seg_gen is stale (key->seg_gen < key->cache_pos.cache_seg->gen), cache_key_put(key) is called but then key->cache_pos.cache_seg is accessed as the argument to cache_seg_get(). This is a use-after-free on the freed key memory. Although mempool recycled memory is not immediately reclaimed or overwritten in practice, this is still a potential UAF bug. Additionally, for expired invalid keys, setting the cache->seg_map bit and calling cache_seg_get() is unreasonable since the corresponding segment data is no longer valid. Fix both issues by moving cache_seg_get() and __set_bit() after the gen check, so they only execute for valid keys, and using continue to skip invalid keys.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0
Version: 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0
Version: 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/md/dm-pcache/cache_key.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "1894fc7a3bab90143dcd26ef8ee27040ef4a7501",
              "status": "affected",
              "version": "1d57628ff95b32d5cfa8d8f50e07690c161e9cf0",
              "versionType": "git"
            },
            {
              "lessThan": "f39a3e9cc5946473e16d6f5071b2ee0216c56d06",
              "status": "affected",
              "version": "1d57628ff95b32d5cfa8d8f50e07690c161e9cf0",
              "versionType": "git"
            },
            {
              "lessThan": "c2e894eac398b258f12fdec73ed6ba081047f7b3",
              "status": "affected",
              "version": "1d57628ff95b32d5cfa8d8f50e07690c161e9cf0",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/md/dm-pcache/cache_key.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
              "lessThan": "6.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndm-pcache: fix use-after-free and invalid seg operations in kset_replay()\n\nIn kset_replay, when key-\u003eseg_gen is stale (key-\u003eseg_gen \u003c\nkey-\u003ecache_pos.cache_seg-\u003egen), cache_key_put(key) is called but then\nkey-\u003ecache_pos.cache_seg is accessed as the argument to cache_seg_get().\nThis is a use-after-free on the freed key memory. Although mempool\nrecycled memory is not immediately reclaimed or overwritten in practice,\nthis is still a potential UAF bug.\n\nAdditionally, for expired invalid keys, setting the cache-\u003eseg_map bit\nand calling cache_seg_get() is unreasonable since the corresponding\nsegment data is no longer valid.\n\nFix both issues by moving cache_seg_get() and __set_bit() after the\ngen check, so they only execute for valid keys, and using continue to\nskip invalid keys."
        }
      ],
      "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 UAF is reached only via local device-mapper ioctls on /dev/mapper/control (ctl_ioctl \u2192 table_load \u2192 dm_pcache_ctr \u2192 pcache_start \u2192 pcache_cache_start \u2192 cache_init_req_keys \u2192 cache_replay \u2192 kset_replay). No network, Bluetooth, or physical-bus path feeds this replay code.\nAC:L - The attacker fully controls the DAX cache-device image, including kset records (CRC uses public PCACHE_CRC_SEED 0x3B15A) and per-segment gen metadata, so they can deterministically encode keys with seg_gen \u003c cache_seg-\u003egen and hit the free-then-use on every table load; no race or victim-side state is required.\nPR:L - ctl_ioctl gates DM_TABLE_LOAD with capable(CAP_SYS_ADMIN), which is obtainable inside an unprivileged user namespace (and in storage containers with delegated mapper/DAX nodes); per kernel CNA guidance that is Low, not init-namespace root only.\nUI:N - Exploitation requires only the attacker\u0027s own dmsetup/DM_TABLE_LOAD of a pcache target whose cache device holds crafted INIT_DONE ksets; no separate victim must mount media, open a file, or otherwise interact.\nS:U - The use-after-free is of a pcache_cache_key in the req_key_tree mempool and of cache seg_map/segment refcounts inside the host kernel; it does not cross a VM, hypervisor, IOMMU, or other separate security-authority boundary.\nC:H - On a stale key, cache_key_put() mempool-frees the decoded pcache_cache_key and kset_replay then reads key-\u003ecache_pos.cache_seg from that freed heap object. A kernel UAF of a slab/mempool object enables reclaim and an arbitrary read primitive, so confidentiality is High.\nI:H - The dangling key is passed to cache_seg_get(), which atomic_inc()s refs on the pointer loaded from freed memory, and the stale path also __set_bit()s cache-\u003eseg_map before the gen check. That UAF write/refcount primitive is Integrity High and is exploitable for control-flow hijack after spraying.\nA:H - Using the freed cache key (and inflating segment refs plus seg_map bits for invalid keys) can oops or panic on poisoned/reused mempool memory or under KASAN/slub debug; any kernel crash from this UAF is Availability High."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:45:39.156Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1894fc7a3bab90143dcd26ef8ee27040ef4a7501"
        },
        {
          "url": "https://git.kernel.org/stable/c/f39a3e9cc5946473e16d6f5071b2ee0216c56d06"
        },
        {
          "url": "https://git.kernel.org/stable/c/c2e894eac398b258f12fdec73ed6ba081047f7b3"
        }
      ],
      "title": "dm-pcache: fix use-after-free and invalid seg operations in kset_replay()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80955",
    "datePublished": "2026-09-11T19:42:23.838Z",
    "dateReserved": "2026-08-26T14:34:25.804Z",
    "dateUpdated": "2026-10-19T08:45:39.156Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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