CVE-2026-98840
Received
Received - Intake
Use-After-Free in Linux Kernel vc_screen Subsystem
Vulnerability report for CVE-2026-98840, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-18
Last updated on: 2026-10-18
Assigner: kernel.org
Description
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 '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().
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| Linux | Linux | 73049768ad57145acd337102c5aa3c788e6642c8 |
| Linux | Linux | 7cc3dd79777f6ae4625ec37e84dd18a26dc88bde |
| Linux | Linux | a287620312dc6dcb9a093417a0e589bf30fcf38a |
| Linux | Linux | a287620312dc6dcb9a093417a0e589bf30fcf38a |
| Linux | Linux | 43a6281790273c1b0a9ab76609ff0245b968f1e6 |
| Linux | Linux | b6bbb85cf45bf0b070e741997fe0af3a772c5ad5 |
| Linux | Linux | ff4806202749a51938236214adc0281481a57366 |
| Linux | Linux | 8232fca738011ca2ec865b46ec721d1796dc0580 |
| Linux | Linux | 74be188eb2dc1c99d63986167b9a67d415fe7326 |
| Linux | Linux | 09a43e81279b8da15526da09877134b8bcf618b0 |
| Linux | Linux | 6.12.95 |
| Linux | Linux | 6.18.37 |
| Linux | Linux | 5.10.260 |
| Linux | Linux | 5.15.211 |
| Linux | Linux | 6.1.177 |
| Linux | Linux | 6.6.144 |
| Linux | Linux | 7.0.14 |
| Linux | Linux | 7.1.2 |
| Linux | Linux | 7.2 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
