CVE-2026-98840
Status: ReceivedUnscored—
Severity—Unscored
Exploitation probability0.17 %higher than 6% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitNot knownno public code found
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.
Read full descriptionShow less
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:
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().
Technical details traces, logs and code from the original report
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)
CVSS
NVD hasn't assigned a CVSS score to this CVE (common since the April 2026 policy change).
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days
- 0.17 %
- Percentile among all scored CVEs
- 6
- Score date
- 10/20/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.
References
Show 4 references
Raw JSON (NVD)
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{
"id": "CVE-2026-98840",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "73049768ad57145acd337102c5aa3c788e6642c8",
"lessThan": "1485a3dd97ab1af2605243cabe6b604546d46dd1",
"versionType": "git"
},
{
"status": "affected",
"version": "7cc3dd79777f6ae4625ec37e84dd18a26dc88bde",
"lessThan": "233a2e190b12884d186027d0b86d43a48799b69c",
"versionType": "git"
},
{
"status": "affected",
"version": "a287620312dc6dcb9a093417a0e589bf30fcf38a",
"lessThan": "9dfcadc5e003fb250dd471db90144bd5366140e9",
"versionType": "git"
},
{
"status": "affected",
"version": "a287620312dc6dcb9a093417a0e589bf30fcf38a",
"lessThan": "226bd5603371cd9f6642cbb9e9a677f445de3530",
"versionType": "git"
},
{
"status": "affected",
"version": "43a6281790273c1b0a9ab76609ff0245b968f1e6",
"versionType": "git"
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{
"status": "affected",
"version": "b6bbb85cf45bf0b070e741997fe0af3a772c5ad5",
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},
{
"status": "affected",
"version": "ff4806202749a51938236214adc0281481a57366",
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{
"status": "affected",
"version": "8232fca738011ca2ec865b46ec721d1796dc0580",
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},
{
"status": "affected",
"version": "74be188eb2dc1c99d63986167b9a67d415fe7326",
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{
"status": "affected",
"version": "09a43e81279b8da15526da09877134b8bcf618b0",
"versionType": "git"
},
{
"status": "affected",
"version": "6.12.95",
"lessThan": "6.12.113",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.18.37",
"lessThan": "6.18.56",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.10.260",
"lessThan": "5.11",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.15.211",
"lessThan": "5.16",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.1.177",
"lessThan": "6.2",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.6.144",
"lessThan": "6.7",
"versionType": "semver"
},
{
"status": "affected",
"version": "7.0.14",
"lessThan": "7.1",
"versionType": "semver"
},
{
"status": "affected",
"version": "7.1.2",
"lessThan": "7.2",
"versionType": "semver"
}
],
"programFiles": [
"drivers/tty/vt/vc_screen.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7.2"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "7.2",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.113",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.56",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.10",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/tty/vt/vc_screen.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-10-18T16:17:38.293",
"references": [
{
"url": "https://git.kernel.org/stable/c/1485a3dd97ab1af2605243cabe6b604546d46dd1",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/226bd5603371cd9f6642cbb9e9a677f445de3530",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/233a2e190b12884d186027d0b86d43a48799b69c",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/9dfcadc5e003fb250dd471db90144bd5366140e9",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "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 'vc' added by commit 8fb9ea65c9d1 (\"vc_screen: reload load\nof struct vc_data pointer in vcs_write() to avoid UAF\") sits after the\n'if (ret)' block, so the copy-failure break path exits the loop without\nreloading vc. If the vc was kfree()'d via vc_port_destruct during the\nunlocked copy_from_user() window, the post-loop\n'if (written && vc) vcs_scr_updated(vc)' is reached with a stale\nnon-NULL vc. The '&& vc' 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->vc->vc_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 -> con_install -> tty_open\n Freed by task: kfree <- vt_ioctl (VT_DISALLOCATE -> vc_port_destruct)\n\nMove the reload to immediately after console_lock(), before 'if (ret)',\nso every break path below passes a fresh vc to the post-loop\nvcs_scr_updated()."
}
],
"lastModified": "2026-10-19T10:19:48.077",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}