{
  "cveId": "CVE-2026-98840",
  "url": "https://patchblox.com/security/cve/CVE-2026-98840",
  "summary": "CVE-2026-98840 is fixed in 49 products on 1 platform, first by DEBIAN-CVE-2026-98840, released October 19, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "vc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF",
  "description": "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 \u0027vc\u0027 added by commit 8fb9ea65c9d1 (\u0022vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF\u0022) sits after the \u0027if (ret)\u0027 block, so the copy-failure break path exits the loop without reloading vc. If the vc was kfree()\u0027d via vc_port_destruct during the unlocked copy_from_user() window, the post-loop \u0027if (written \u0026\u0026 vc) vcs_scr_updated(vc)\u0027 is reached with a stale non-NULL vc. The \u0027\u0026\u0026 vc\u0027 guard from commit a287620312dc (\u0022vc_screen: fix null-ptr-deref in vcs_notifier() during concurrent vcs_write\u0022) only handles the NULL case, not this stale-non-NULL case; vcs_notifier() then reads param-\u003Evc-\u003Evc_num from freed memory:    BUG: KASAN: slab-use-after-free in vcs_notifier\u002B0x7c/0xd0   Read of size 2 at addr ffff888007149190   Call Trace:    vcs_notifier\u002B0x7c/0xd0    atomic_notifier_call_chain\u002B0x70/0xa0    vcs_scr_updated\u002B0x77/0xa0    vcs_write\u002B0x71b/0x7e0   Allocated by task: vc_allocate -\u003E con_install -\u003E tty_open   Freed by task: kfree \u003C- vt_ioctl (VT_DISALLOCATE -\u003E vc_port_destruct)  Move the reload to immediately after console_lock(), before \u0027if (ret)\u0027, so every break path below passes a fresh vc to the post-loop vcs_scr_updated().",
  "published": "2026-10-18T16:17:38Z",
  "severity": "Moderate",
  "cvss": 4.7,
  "epss": 0.00176,
  "epssPercentile": 0.07202,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98840",
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