---
id: CVE-2026-98840
title: 'vc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF'
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 poi…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 73049768ad57145acd337102c5aa3c788e6642c8 <
    1485a3dd97ab1af2605243cabe6b604546d46dd1
  - >-
    Linux >= 7cc3dd79777f6ae4625ec37e84dd18a26dc88bde <
    233a2e190b12884d186027d0b86d43a48799b69c
  - >-
    Linux >= a287620312dc6dcb9a093417a0e589bf30fcf38a <
    9dfcadc5e003fb250dd471db90144bd5366140e9
  - >-
    Linux >= a287620312dc6dcb9a093417a0e589bf30fcf38a <
    226bd5603371cd9f6642cbb9e9a677f445de3530
  - Linux 43a6281790273c1b0a9ab76609ff0245b968f1e6
  - Linux b6bbb85cf45bf0b070e741997fe0af3a772c5ad5
  - Linux ff4806202749a51938236214adc0281481a57366
  - Linux 8232fca738011ca2ec865b46ec721d1796dc0580
  - Linux 74be188eb2dc1c99d63986167b9a67d415fe7326
  - Linux 09a43e81279b8da15526da09877134b8bcf618b0
  - Linux >= 6.12.95 < 6.12.113
  - Linux >= 6.18.37 < 6.18.56
  - Linux >= 5.10.260 < 5.11
  - Linux >= 5.15.211 < 5.16
  - Linux >= 6.1.177 < 6.2
  - Linux >= 6.6.144 < 6.7
  - Linux >= 7.0.14 < 7.1
  - Linux >= 7.1.2 < 7.2
  - Linux 7.2
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T15:50:14.029Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-98840'
references:
  - url: 'https://git.kernel.org/stable/c/1485a3dd97ab1af2605243cabe6b604546d46dd1'
  - url: 'https://git.kernel.org/stable/c/233a2e190b12884d186027d0b86d43a48799b69c'
  - url: 'https://git.kernel.org/stable/c/9dfcadc5e003fb250dd471db90144bd5366140e9'
  - url: 'https://git.kernel.org/stable/c/226bd5603371cd9f6642cbb9e9a677f445de3530'
tags:
  - cve.org
ingestedAt: '2026-10-18T16:47:32.468Z'
---

## Overview

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().

## Affected

- `Linux >= 73049768ad57145acd337102c5aa3c788e6642c8 < 1485a3dd97ab1af2605243cabe6b604546d46dd1`
- `Linux >= 7cc3dd79777f6ae4625ec37e84dd18a26dc88bde < 233a2e190b12884d186027d0b86d43a48799b69c`
- `Linux >= a287620312dc6dcb9a093417a0e589bf30fcf38a < 9dfcadc5e003fb250dd471db90144bd5366140e9`
- `Linux >= a287620312dc6dcb9a093417a0e589bf30fcf38a < 226bd5603371cd9f6642cbb9e9a677f445de3530`
- `Linux 43a6281790273c1b0a9ab76609ff0245b968f1e6`
- `Linux b6bbb85cf45bf0b070e741997fe0af3a772c5ad5`
- `Linux ff4806202749a51938236214adc0281481a57366`
- `Linux 8232fca738011ca2ec865b46ec721d1796dc0580`
- `Linux 74be188eb2dc1c99d63986167b9a67d415fe7326`
- `Linux 09a43e81279b8da15526da09877134b8bcf618b0`
- `Linux >= 6.12.95 < 6.12.113`
- `Linux >= 6.18.37 < 6.18.56`
- `Linux >= 5.10.260 < 5.11`
- `Linux >= 5.15.211 < 5.16`
- `Linux >= 6.1.177 < 6.2`
- `Linux >= 6.6.144 < 6.7`
- `Linux >= 7.0.14 < 7.1`
- `Linux >= 7.1.2 < 7.2`
- `Linux 7.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.