VulnerabilityPublished 18 Oct 2026

CVE-2026-98628: Linux kernel · bpf: Make post-verification instruction rewrites killable

Affects Linux kernelSource CVE Database V5

Not known to be exploited : upgrade to 261b61d3735b042ae25634f795c4540be0fc140c or 56dc616d7a1f7d134d3e101c455e62b0a24d0cfd when convenient.

Data as of 26 Oct 2026, 12:55 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 261b61d3735b042ae25634f795c4540be0fc140c, 56dc616d7a1f7d134d3e101c455e62b0a24d0cfd

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.

What to do

Upgrade Linux kernel to 261b61d3735b042ae25634f795c4540be0fc140c or 56dc616d7a1f7d134d3e101c455e62b0a24d0cfd.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 52875a04f4b26e7ef30a288ea096f7cfec0e93cd, < 261b61d3735b042ae25634f795c4540be0fc140c	Fixed in 261b61d3735b042ae25634f795c4540be0fc140c
LinuxLinux	Affected ≥ 52875a04f4b26e7ef30a288ea096f7cfec0e93cd, < 56dc616d7a1f7d134d3e101c455e62b0a24d0cfd	Fixed in 56dc616d7a1f7d134d3e101c455e62b0a24d0cfd
LinuxLinux	Affected =5.1	Fixed in–

AI-suggested

This vulnerability has been fixed in Linux kernel versions identified by commits 261b61d3735b042ae25634f795c4540be0fc140c and 56dc616d7a1f7d134d3e101c455e62b0a24d0cfd. Users should update to these or later kernel versions to apply the official fix. No additional mitigation is required as the patch enables proper cancellation and rescheduling during the rewrite passes.

Description

A vulnerability in the Linux kernel's BPF verifier post-verification instruction rewrite process could cause a privileged loader task to become unkillable during lengthy rewrites. The issue arises because the rewrite passes do not check for signals or reschedule, preventing termination signals like SIGKILL from interrupting the task. The fix introduces cancellation and rescheduling points to make the rewrite process preemptible, allowing prompt termination of killed loaders.

Impact

A privileged user loading BPF programs could cause the kernel verifier's post-verification rewrites to run for a long time without responding to termination signals, making the loader process unkillable until the rewrites complete. This could lead to denial of service conditions for that process. The fix allows the kernel to promptly terminate such tasks, improving system responsiveness and stability.

Summary

The Linux kernel's BPF verifier performs several instruction rewrite passes after verification, which involve patching or removing instructions one at a time. This process is quadratic in program length and does not check for signals or reschedule, causing a privileged loader submitting many unconditional jumps to become unkillable during the rewrite phase. The patch makes the rewrite helpers bpf_patch_insn_data() and verifier_remove_insns() support cancellation and rescheduling, enabling interruption and prompt task termination. Interrupted constant blinding returns -EINTR and is propagated through JIT paths, improving responsiveness without reducing the quadratic complexity of the rewrites.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 10:08 UTC

Technical details

References

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