GHSA-VPW3-5QWQ-WXVW
Vulnerability from github – Published: 2026-10-18 18:32 – Updated: 2026-10-18 18:32In 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": [],
"aliases": [
"CVE-2026-98840"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-18T16:17:38Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nvc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF\n\nThe reload of \u0027vc\u0027 added by commit 8fb9ea65c9d1 (\"vc_screen: reload load\nof struct vc_data pointer in vcs_write() to avoid UAF\") sits after the\n\u0027if (ret)\u0027 block, so the copy-failure break path exits the loop without\nreloading vc. If the vc was kfree()\u0027d via vc_port_destruct during the\nunlocked copy_from_user() window, the post-loop\n\u0027if (written \u0026\u0026 vc) vcs_scr_updated(vc)\u0027 is reached with a stale\nnon-NULL vc. The \u0027\u0026\u0026 vc\u0027 guard from commit a287620312dc (\"vc_screen:\nfix null-ptr-deref in vcs_notifier() during concurrent vcs_write\") only\nhandles the NULL case, not this stale-non-NULL case; vcs_notifier() then\nreads param-\u003evc-\u003evc_num from freed memory:\n\n BUG: KASAN: slab-use-after-free in vcs_notifier+0x7c/0xd0\n Read of size 2 at addr ffff888007149190\n Call Trace:\n vcs_notifier+0x7c/0xd0\n atomic_notifier_call_chain+0x70/0xa0\n vcs_scr_updated+0x77/0xa0\n vcs_write+0x71b/0x7e0\n Allocated by task: vc_allocate -\u003e con_install -\u003e tty_open\n Freed by task: kfree \u003c- vt_ioctl (VT_DISALLOCATE -\u003e vc_port_destruct)\n\nMove the reload to immediately after console_lock(), before \u0027if (ret)\u0027,\nso every break path below passes a fresh vc to the post-loop\nvcs_scr_updated().",
"id": "GHSA-vpw3-5qwq-wxvw",
"modified": "2026-10-18T18:32:05Z",
"published": "2026-10-18T18:32:05Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98840"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1485a3dd97ab1af2605243cabe6b604546d46dd1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/226bd5603371cd9f6642cbb9e9a677f445de3530"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/233a2e190b12884d186027d0b86d43a48799b69c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9dfcadc5e003fb250dd471db90144bd5366140e9"
}
],
"schema_version": "1.4.0",
"severity": []
}
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
Loading timeline…
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.