VulnerabilityPublished 18 Oct 2026

CVE-2026-98839: Linux kernel · vt: selection: Fix unsigned underflow and slab-out-of-bounds read in paste_selection()

Source GCVE Database

Authoritative record:CVE-2026-98839· High

Not known to be exploited · fixed in 39495ef5d6f8019e62d65807f217a7ca8232727a : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

Severity

High

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 39495ef5d6f8019e62d65807f217a7ca8232727a, 619c6d7dd76fff15a9714fbf02ce299b737f01a2, 037d7e3ca5c593092f4b0d471eb869a85cbddde0 +7

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-rgr5-hhj8-qq6p

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected >=3.16.83 <3.17 >=4.4.216 <4.5 >=4.9.216 <4.10 >=4.14.173 <4.15 >=4.19.109 <4.20 >=5.4.25 <5.5 >=5.5.9 <5.6	Fixed in 39495ef5d6f8019e62d65807f217a7ca8232727a 619c6d7dd76fff15a9714fbf02ce299b737f01a2 037d7e3ca5c593092f4b0d471eb869a85cbddde0 5.6 5.5 4.20 4.15 4.10 4.5 3.17
LinuxLinux	Affected =5.6	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel to terminate the loop in paste_selection() when the pasted counter reaches or exceeds the buffer length, preventing the unsigned underflow and out-of-bounds read. Users should apply the official kernel update containing this fix once available. No other mitigations are indicated.

Description

A vulnerability in the Linux kernel's virtual terminal (vt) selection code was fixed to address an unsigned integer underflow and slab-out-of-bounds read in the paste_selection() function. The issue arises when a concurrent ioctl call modifies the selection buffer length while paste_selection() is running, causing an underflow and out-of-bounds memory read. This flaw was resolved by adding a loop termination condition to prevent reading beyond the buffer.

Impact

The vulnerability can cause out-of-bounds reads in kernel memory, potentially leading to kernel crashes or memory corruption. Although no active exploits are known, such memory safety issues can be leveraged for denial of service or potentially privilege escalation in certain contexts.

Summary

The vulnerability in the Linux kernel's vt selection subsystem involves the paste_selection() function, which copies data from a selection buffer to the tty line discipline receive buffer. The function uses a loop that copies a calculated number of bytes per iteration and increments a 'pasted' counter. However, the selection mutex is released inside the loop, allowing a concurrent TIOCLINUX ioctl to replace the selection buffer with a shorter one and reduce its length below the current 'pasted' value. When paste_selection() resumes, the subtraction vc_sel.buf_len - pasted underflows as an unsigned integer, resulting in a large positive value. This causes tty_ldisc_receive_buf() to read up to 4094 bytes out-of-bounds past the buffer, leading to a slab-out-of-bounds read detected by KASAN. The fix terminates the loop when pasted is greater than or equal to vc_sel.buf_len, preventing the underflow and out-of-bounds access.

References

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