VulnerabilityPublished 18 Oct 2026

CVE-2026-98540: Linux kernel · fprobe: Terminate the fgraph_data list when the reservation is not filled

Affects Linux kernelSource CVE Database V5

Not known to be exploited : upgrade to b7459fddcb27a4b7d01067678172afa362cf660d or 1d653a183973f5283a3db5a38cd5e195eb152244 when convenient.

Data as of 26 Oct 2026, 17:16 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 b7459fddcb27a4b7d01067678172afa362cf660d, 1d653a183973f5283a3db5a38cd5e195eb152244

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 b7459fddcb27a4b7d01067678172afa362cf660d or 1d653a183973f5283a3db5a38cd5e195eb152244.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ e0a384434ae1bdfb03954c46c464e3dbd3223ad6, < b7459fddcb27a4b7d01067678172afa362cf660d	Fixed in b7459fddcb27a4b7d01067678172afa362cf660d
LinuxLinux	Affected ≥ e0a384434ae1bdfb03954c46c464e3dbd3223ad6, < 1d653a183973f5283a3db5a38cd5e195eb152244	Fixed in 1d653a183973f5283a3db5a38cd5e195eb152244
LinuxLinux	Affected =7.1	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel, as indicated by the fixed commit versions. Users should update to the fixed kernel versions to remediate this issue.

Description

A vulnerability in the Linux kernel's fprobe feature was fixed by ensuring proper termination of the fgraph_data list when reservation space is not fully used. The flaw caused the exit handler to potentially run twice or run despite being skipped, due to parsing leftover headers from previous calls.

Impact

This vulnerability could cause an exit handler to run twice or run when it should be skipped, potentially leading to unexpected kernel behavior or instability. There is no indication of exploitation in the wild or direct security compromise from the provided data.

Summary

The Linux kernel's fprobe_fgraph_entry() function reserves shadow stack space for each fprobe with an exit handler but only fills it when the entry handler returns 0. Because fgraph_reserve_data() does not clear unused reserved space, fprobe_return() misinterprets leftover data as valid headers, causing an exit handler to execute multiple times or unexpectedly. The fix involves writing a zero word after the last valid entry to terminate the list properly, ensuring that zeroed slots are correctly interpreted as NULL and preventing erroneous exit handler execution.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 10:40 UTC

Technical details

References

Community reviews

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