CVE-2026-98840: Linux Vulnerability

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().

Metrics

EPSS Probability

0.17%

6.0th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 43a6281790273c1b0a9ab76609ff0245b968f1e6, < cbc05413d3694193494b2374b56bae801ac41fec; >= b6bbb85cf45bf0b070e741997fe0af3a772c5ad5, < 942742000a0288d4ca60c448894aabacd48004d5; >= ff4806202749a51938236214adc0281481a57366, < c9f56d4b29792a62b17f2051ba93fd3b40a479ec; >= 8232fca738011ca2ec865b46ec721d1796dc0580, < c073d01f6f5367c3a4f07efd507274ed0d03acd0; >= 73049768ad57145acd337102c5aa3c788e6642c8, < 1485a3dd97ab1af2605243cabe6b604546d46dd1; >= 7cc3dd79777f6ae4625ec37e84dd18a26dc88bde, < 233a2e190b12884d186027d0b86d43a48799b69c; >= a287620312dc6dcb9a093417a0e589bf30fcf38a, < 9dfcadc5e003fb250dd471db90144bd5366140e9; >= a287620312dc6dcb9a093417a0e589bf30fcf38a, < 226bd5603371cd9f6642cbb9e9a677f445de3530; 74be188eb2dc1c99d63986167b9a67d415fe7326; 09a43e81279b8da15526da09877134b8bcf618b0; >= 5.10.260, < 5.10.273; >= 5.15.211, < 5.15.224; >= 6.1.177, < 6.1.191; >= 6.6.144, < 6.6.160; >= 6.12.95, < 6.12.113; >= 6.18.37, < 6.18.56; >= 7.0.14, < 7.1; >= 7.1.2, < 7.2
Linux	Linux	7.2

References

Timeline

Published: Oct 18, 2026
Last Modified: Oct 30, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-98840?

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().

How severe is CVE-2026-98840?

Severity scoring for CVE-2026-98840 is pending analysis. The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-98840?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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