FKIE_CVE-2026-98840

Vulnerability from fkie_nvd - Published: 2026-10-18 16:17 - Updated: 2026-10-18 16:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: vc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF The reload of 'vc' added by commit 8fb9ea65c9d1 ("vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF") sits after the 'if (ret)' block, so the copy-failure break path exits the loop without reloading vc. If the vc was kfree()'d via vc_port_destruct during the unlocked copy_from_user() window, the post-loop 'if (written && vc) vcs_scr_updated(vc)' is reached with a stale non-NULL vc. The '&& vc' guard from commit a287620312dc ("vc_screen: fix null-ptr-deref in vcs_notifier() during concurrent vcs_write") only handles the NULL case, not this stale-non-NULL case; vcs_notifier() then reads param->vc->vc_num from freed memory: BUG: KASAN: slab-use-after-free in vcs_notifier+0x7c/0xd0 Read of size 2 at addr ffff888007149190 Call Trace: vcs_notifier+0x7c/0xd0 atomic_notifier_call_chain+0x70/0xa0 vcs_scr_updated+0x77/0xa0 vcs_write+0x71b/0x7e0 Allocated by task: vc_allocate -> con_install -> tty_open Freed by task: kfree <- vt_ioctl (VT_DISALLOCATE -> vc_port_destruct) Move the reload to immediately after console_lock(), before 'if (ret)', so every break path below passes a fresh vc to the post-loop vcs_scr_updated().
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1485a3dd97ab1af2605243cabe6b604546d46dd1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/226bd5603371cd9f6642cbb9e9a677f445de3530
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/233a2e190b12884d186027d0b86d43a48799b69c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9dfcadc5e003fb250dd471db90144bd5366140e9
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/tty/vt/vc_screen.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "1485a3dd97ab1af2605243cabe6b604546d46dd1",
              "status": "affected",
              "version": "73049768ad57145acd337102c5aa3c788e6642c8",
              "versionType": "git"
            },
            {
              "lessThan": "233a2e190b12884d186027d0b86d43a48799b69c",
              "status": "affected",
              "version": "7cc3dd79777f6ae4625ec37e84dd18a26dc88bde",
              "versionType": "git"
            },
            {
              "lessThan": "9dfcadc5e003fb250dd471db90144bd5366140e9",
              "status": "affected",
              "version": "a287620312dc6dcb9a093417a0e589bf30fcf38a",
              "versionType": "git"
            },
            {
              "lessThan": "226bd5603371cd9f6642cbb9e9a677f445de3530",
              "status": "affected",
              "version": "a287620312dc6dcb9a093417a0e589bf30fcf38a",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "43a6281790273c1b0a9ab76609ff0245b968f1e6",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "b6bbb85cf45bf0b070e741997fe0af3a772c5ad5",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ff4806202749a51938236214adc0281481a57366",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "8232fca738011ca2ec865b46ec721d1796dc0580",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "74be188eb2dc1c99d63986167b9a67d415fe7326",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "09a43e81279b8da15526da09877134b8bcf618b0",
              "versionType": "git"
            },
            {
              "lessThan": "6.12.113",
              "status": "affected",
              "version": "6.12.95",
              "versionType": "semver"
            },
            {
              "lessThan": "6.18.56",
              "status": "affected",
              "version": "6.18.37",
              "versionType": "semver"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.260",
              "versionType": "semver"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.211",
              "versionType": "semver"
            },
            {
              "lessThan": "6.2",
              "status": "affected",
              "version": "6.1.177",
              "versionType": "semver"
            },
            {
              "lessThan": "6.7",
              "status": "affected",
              "version": "6.6.144",
              "versionType": "semver"
            },
            {
              "lessThan": "7.1",
              "status": "affected",
              "version": "7.0.14",
              "versionType": "semver"
            },
            {
              "lessThan": "7.2",
              "status": "affected",
              "version": "7.1.2",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/tty/vt/vc_screen.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.2"
            },
            {
              "lessThan": "7.2",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.113",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.56",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc6",
              "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\nvc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF\n\nThe reload of \u0027vc\u0027 added by commit 8fb9ea65c9d1 (\"vc_screen: reload load\nof struct vc_data pointer in vcs_write() to avoid UAF\") sits after the\n\u0027if (ret)\u0027 block, so the copy-failure break path exits the loop without\nreloading vc. If the vc was kfree()\u0027d via vc_port_destruct during the\nunlocked copy_from_user() window, the post-loop\n\u0027if (written \u0026\u0026 vc) vcs_scr_updated(vc)\u0027 is reached with a stale\nnon-NULL vc. The \u0027\u0026\u0026 vc\u0027 guard from commit a287620312dc (\"vc_screen:\nfix null-ptr-deref in vcs_notifier() during concurrent vcs_write\") only\nhandles the NULL case, not this stale-non-NULL case; vcs_notifier() then\nreads param-\u003evc-\u003evc_num from freed memory:\n\n  BUG: KASAN: slab-use-after-free in vcs_notifier+0x7c/0xd0\n  Read of size 2 at addr ffff888007149190\n  Call Trace:\n   vcs_notifier+0x7c/0xd0\n   atomic_notifier_call_chain+0x70/0xa0\n   vcs_scr_updated+0x77/0xa0\n   vcs_write+0x71b/0x7e0\n  Allocated by task: vc_allocate -\u003e con_install -\u003e tty_open\n  Freed by task: kfree \u003c- vt_ioctl (VT_DISALLOCATE -\u003e vc_port_destruct)\n\nMove the reload to immediately after console_lock(), before \u0027if (ret)\u0027,\nso every break path below passes a fresh vc to the post-loop\nvcs_scr_updated()."
    }
  ],
  "id": "CVE-2026-98840",
  "lastModified": "2026-10-18T16:17:38.293",
  "metrics": {},
  "published": "2026-10-18T16:17:38.293",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1485a3dd97ab1af2605243cabe6b604546d46dd1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/226bd5603371cd9f6642cbb9e9a677f445de3530"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/233a2e190b12884d186027d0b86d43a48799b69c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9dfcadc5e003fb250dd471db90144bd5366140e9"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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