CVE-2026-98840

vc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF

State: Published
Severity: Not scored
Published: Oct 18, 2026
Updated: Oct 30, 2026
Reserved: Sep 25, 2026

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().

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	43a6281790273c1b0a9ab76609ff0245b968f1e6 to before cbc05413d3694193494b2374b56bae801ac41fecAffected b6bbb85cf45bf0b070e741997fe0af3a772c5ad5 to before 942742000a0288d4ca60c448894aabacd48004d5Affected ff4806202749a51938236214adc0281481a57366 to before c9f56d4b29792a62b17f2051ba93fd3b40a479ecAffected 8232fca738011ca2ec865b46ec721d1796dc0580 to before c073d01f6f5367c3a4f07efd507274ed0d03acd0Affected 73049768ad57145acd337102c5aa3c788e6642c8 to before 1485a3dd97ab1af2605243cabe6b604546d46dd1Affected 7cc3dd79777f6ae4625ec37e84dd18a26dc88bde to before 233a2e190b12884d186027d0b86d43a48799b69cAffected a287620312dc6dcb9a093417a0e589bf30fcf38a to before 9dfcadc5e003fb250dd471db90144bd5366140e9Affected a287620312dc6dcb9a093417a0e589bf30fcf38a to before 226bd5603371cd9f6642cbb9e9a677f445de3530Affected 74be188eb2dc1c99d63986167b9a67d415fe7326Affected 09a43e81279b8da15526da09877134b8bcf618b0Affected 5.10.260 to before 5.10.273Affected 5.15.211 to before 5.15.224Affected 6.1.177 to before 6.1.191Affected 6.6.144 to before 6.6.160Affected 6.12.95 to before 6.12.113Affected 6.18.37 to before 6.18.56Affected 7.0.14 to before 7.1Affected 7.1.2 to before 7.2Affected
LinuxLinux	7.2Affected before 7.2Not affected 5.10.273 through 5.10.Not affected 5.15.224 through 5.15.Not affected 6.1.191 through 6.1.Not affected 6.6.160 through 6.6.Not affected 6.12.113 through 6.12.Not affected 6.18.56 through 6.18.Not affected 7.2.10 through 7.2.*Not affected 7.3 and laterNot affected

Product

Versions

LinuxLinux

43a6281790273c1b0a9ab76609ff0245b968f1e6 to before cbc05413d3694193494b2374b56bae801ac41fecAffected
b6bbb85cf45bf0b070e741997fe0af3a772c5ad5 to before 942742000a0288d4ca60c448894aabacd48004d5Affected
ff4806202749a51938236214adc0281481a57366 to before c9f56d4b29792a62b17f2051ba93fd3b40a479ecAffected
8232fca738011ca2ec865b46ec721d1796dc0580 to before c073d01f6f5367c3a4f07efd507274ed0d03acd0Affected
73049768ad57145acd337102c5aa3c788e6642c8 to before 1485a3dd97ab1af2605243cabe6b604546d46dd1Affected
7cc3dd79777f6ae4625ec37e84dd18a26dc88bde to before 233a2e190b12884d186027d0b86d43a48799b69cAffected
a287620312dc6dcb9a093417a0e589bf30fcf38a to before 9dfcadc5e003fb250dd471db90144bd5366140e9Affected
a287620312dc6dcb9a093417a0e589bf30fcf38a to before 226bd5603371cd9f6642cbb9e9a677f445de3530Affected
74be188eb2dc1c99d63986167b9a67d415fe7326Affected
09a43e81279b8da15526da09877134b8bcf618b0Affected
5.10.260 to before 5.10.273Affected
5.15.211 to before 5.15.224Affected
6.1.177 to before 6.1.191Affected
6.6.144 to before 6.6.160Affected
6.12.95 to before 6.12.113Affected
6.18.37 to before 6.18.56Affected
7.0.14 to before 7.1Affected
7.1.2 to before 7.2Affected

LinuxLinux

7.2Affected
before 7.2Not affected
5.10.273 through 5.10.*Not affected
5.15.224 through 5.15.*Not affected
6.1.191 through 6.1.*Not affected
6.6.160 through 6.6.*Not affected
6.12.113 through 6.12.*Not affected
6.18.56 through 6.18.*Not affected
7.2.10 through 7.2.*Not affected
7.3 and laterNot affected

References

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