VulnerabilityPublished 18 Oct 2026

CVE-2026-98631: Linux kernel · xsk: Use a 32-bit compare in xsk_map_gen_lookup

Source GCVE Database

Authoritative record:CVE-2026-98631· Medium

Not known to be exploited · fixed in c6d5c582d55a8f229d75e98d62eaa065b0deb18d : update Linux kernel when convenient.

Data as of 26 Oct 2026, 14:05 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in c6d5c582d55a8f229d75e98d62eaa065b0deb18d, b5c0cff0c5331582ab01c4c423731453a8381acc, 70504de0bb627848667207bec7ccfd647deb8814 +5

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-r8m8-f9qq-5h53

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ e65650f291ee72fc578d6346080fc4699204ef2c, < c6d5c582d55a8f229d75e98d62eaa065b0deb18d	Fixed in c6d5c582d55a8f229d75e98d62eaa065b0deb18d
LinuxLinux	Affected ≥ e65650f291ee72fc578d6346080fc4699204ef2c, < b5c0cff0c5331582ab01c4c423731453a8381acc	Fixed in b5c0cff0c5331582ab01c4c423731453a8381acc
LinuxLinux	Affected ≥ e65650f291ee72fc578d6346080fc4699204ef2c, < 70504de0bb627848667207bec7ccfd647deb8814	Fixed in 70504de0bb627848667207bec7ccfd647deb8814
LinuxLinux	Affected ≥ e65650f291ee72fc578d6346080fc4699204ef2c, < 36461e58f88a1b723f86693f437ac12e60ff4363	Fixed in 36461e58f88a1b723f86693f437ac12e60ff4363
LinuxLinux	Affected ≥ e65650f291ee72fc578d6346080fc4699204ef2c, < 227ec890559e922e235eb543646e3bf0bd8269b0	Fixed in 227ec890559e922e235eb543646e3bf0bd8269b0
LinuxLinux	Affected ≥ e65650f291ee72fc578d6346080fc4699204ef2c, < 123f90f394ca404ab8796a7c8072ff7fa5b65a9c	Fixed in 123f90f394ca404ab8796a7c8072ff7fa5b65a9c

AI-suggested

A fix has been applied to the Linux kernel to use a 32-bit unsigned comparison (BPF_JMP32_IMM) in xsk_map_gen_lookup, preventing out-of-range index access. Users should update to the patched kernel version once available.

Description

A vulnerability in the Linux kernel's xsk_map_gen_lookup function was resolved. The issue involved improper comparison of a 32-bit key with max_entries using a sign-extended 64-bit immediate, which could cause the bounds check to be bypassed. This allowed out-of-range index access leading to a read past the xsk_map array. The fix involved using a 32-bit unsigned comparison to maintain correct bounds checking.

Impact

The vulnerability could lead to out-of-bounds reads in kernel memory due to improper bounds checking in the xsk_map_gen_lookup function. This could potentially cause information disclosure or kernel instability. No known exploits in the wild have been reported.

Summary

The Linux kernel's xsk_map_gen_lookup function loaded a 32-bit key and compared it with max_entries using BPF_JMP_IMM, which sign-extends immediates to 64 bits. When max_entries was 0x80000000 or higher, the threshold became larger than any zero-extended 32-bit key, causing the bounds check to be skipped. This resulted in an out-of-range index and a read beyond the xsk_map array. The vulnerability was fixed by switching the comparison to BPF_JMP32_IMM, ensuring the check remains within the 32-bit unsigned range.

References

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