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CVE-2026-98840— vc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： vc_screen：在 vcs_write() 函数中，于 判断之前重新加载 vc 指针，以避免“释放后使用”（Use-After-Free, UAF）问题。 此前，由提交 8fb9ea65c9d1（"vc_screen: 在 vcs_write() 中重新加载 struct vc_data 指针以规避 UAF"）所添加的 指针重新加载操作，被置于 代码块之后。因此，当因复制失败而触发 退出循环时， 指针并未被重新加载。若在未加锁的 窗口期间， 已通过 调用 被释放，则

AI Predicted 7.8 Difficulty: Moderate EPSS 0.17% · P6

Affected Version Matrix 24

VendorProduct Version RangeStatus
Linux Linux 73049768ad57145acd337102c5aa3c788e6642c8< 1485a3dd97ab1af2605243cabe6b604546d46dd1 affected
7cc3dd79777f6ae4625ec37e84dd18a26dc88bde< 233a2e190b12884d186027d0b86d43a48799b69c affected
a287620312dc6dcb9a093417a0e589bf30fcf38a< 9dfcadc5e003fb250dd471db90144bd5366140e9 affected
a287620312dc6dcb9a093417a0e589bf30fcf38a< 226bd5603371cd9f6642cbb9e9a677f445de3530 affected
43a6281790273c1b0a9ab76609ff0245b968f1e6 affected
b6bbb85cf45bf0b070e741997fe0af3a772c5ad5 affected
ff4806202749a51938236214adc0281481a57366 affected
8232fca738011ca2ec865b46ec721d1796dc0580 affected
… +16 more rows
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I. Basic Information for CVE-2026-98840

Vulnerability Information
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Vulnerability Title
vc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF
Source: CVE Program / CVE List V5
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().
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 73049768ad57145acd337102c5aa3c788e6642c8 ~ 1485a3dd97ab1af2605243cabe6b604546d46dd1 -
Linux Linux 7.2 -

II. Public POCs for CVE-2026-98840

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III. Intelligence Information for CVE-2026-98840

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Patches & Fixes for CVE-2026-98840 (3)

Same Patch Batch · Linux · 2026-10-18 · 435 CVEs total

CVE-2026-98719 KVM: SEV: Nullify "have run CPUs" mask pointer when freeing it
CVE-2026-98732 Bluetooth: btintel: fix buffer over-read in btintel_hw_error()
CVE-2026-98731 Bluetooth: btintel_pcie: fix plen overflow in btintel_pcie_recv_frame()
CVE-2026-98730 Bluetooth: btintel_pcie: reject oversized TX packets in send_frame()
CVE-2026-98729 x86/mm: Don't apply va_align to hugetlb mappings on AMD F15h
CVE-2026-98728 tpm: fix off-by-four bounds check in tpm2_get_random()
CVE-2026-98727 nvme-multipath: set BLK_FEAT_ZONED only after the zone info is known
CVE-2026-98726 nvme-multipath: fix underflow in ANA log bounds checks
CVE-2026-98725 nvmet-auth: fix out-of-bounds write in nvmet_auth_challenge()
CVE-2026-98724 nvmet: pci-epf: reject too-short SGL segments
CVE-2026-98723 nvmet: copy the hostid into the ctrl before creating PR pc_refs
CVE-2026-98722 mtd: block2mtd: Fix divide error when erase_size is zero
CVE-2026-98721 mtd: rawnand: cadence: Initialize IRQ state before requesting IRQ
CVE-2026-98720 KVM: nVMX: Force MSR bitmap refresh if runtime eVMCS controls are modified
CVE-2026-98707 wifi: mac80211: shut down RX BA session timer on teardown
CVE-2026-98711 wifi: cw1200: fix TX padding OOB read leaking heap data to device
CVE-2026-98710 wifi: iwlegacy: 3945: free EEPROM data on remove
CVE-2026-98709 wifi: mac80211: count only matching reservations in reserved switch
CVE-2026-98712 KVM: arm64: vgic: Take a refcount on IRQs referenced by last_lr_irq
CVE-2026-98708 wifi: mac80211: keep paired old chanctx alive

Showing top 20 of 435 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-98840

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