VulnerabilityPublished 18 Oct 2026Updated 28 Oct 2026

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

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-98540· Medium

Not known to be exploited.

Data as of 29 Oct 2026, 01:00 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

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

Affected software

Product	Affected	Fixed in
Ubuntu 24.04 LTSlinux-aws-6.14`pkg:deb/ubuntu/linux-aws-6.14?arch=source&distro=noble`Other threats	Affected 6.14.0-1007.7~24.04.1 – 6.14.0-1018.18~24.04.1 11 affected builds	Fixed in–
Ubuntu 24.04 LTSlinux-aws-6.17`pkg:deb/ubuntu/linux-aws-6.17?arch=source&distro=noble`Other threats	Affected 6.17.0-1005.5~24.04.2 – 6.17.0-1020.20~24.04.1 10 affected builds	Fixed in–
Ubuntu 24.04 LTSlinux-azure-6.11`pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=noble`Other threats	Affected 6.11.0-1008.8~24.04.1 – 6.11.0-1018.18~24.04.1 7 affected builds	Fixed in–
Ubuntu 24.04 LTSlinux-azure-6.14`pkg:deb/ubuntu/linux-azure-6.14?arch=source&distro=noble`Other threats	Affected 6.14.0-1010.10~24.04.1 – 6.14.0-1017.17~24.04.1 5 affected builds	Fixed in–
Ubuntu 24.04 LTSlinux-azure-6.17`pkg:deb/ubuntu/linux-azure-6.17?arch=source&distro=noble`Other threats	Affected 6.17.0-1008.8~24.04.1 – 6.17.0-1022.22 10 affected builds	Fixed in–
Ubuntu 24.04 LTSlinux-azure-fde-6.14`pkg:deb/ubuntu/linux-azure-fde-6.14?arch=source&distro=noble`Other threats	Affected 6.14.0-1012.12~24.04.1 – 6.14.0-1017.17~24.04.1 5 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available that properly terminates the fgraph_data list by writing a zero word after the last entry and adjusts the header decoding logic. Users should apply the updated Linux kernel versions that include this fix. No additional mitigation actions are indicated.

Description

A vulnerability in the Linux kernel's fprobe feature causes improper termination of the fgraph_data list when a reservation is not filled. This can lead to an exit handler running twice or running despite being skipped by its entry handler. The issue arises because reserved shadow stack space is not cleared, causing fprobe_return() to misinterpret unused data. The fix involves writing a zero word after the last entry to properly terminate the list and adjusting the header decoding to handle zeroed slots correctly.

Impact

The vulnerability may cause an exit handler to run twice or run unexpectedly, which could lead to unintended behavior in kernel tracing or debugging operations. The severity is low, and there is no indication of exploitation in the wild or direct security compromise beyond potential instability or incorrect tracing results.

Summary

The Linux kernel's fprobe_fgraph_entry() function reserves shadow stack space for every fprobe with an exit handler but only fills it for those whose entry handler returns 0. The fgraph_reserve_data() function does not clear the reserved area, causing fprobe_return() to parse leftover headers from previous calls. This results in an exit handler potentially executing twice or executing despite its entry handler requesting to skip it. The vulnerability is addressed by writing a zero word after the last entry to terminate the walk and modifying read_fprobe_header() to return NULL for zeroed slots, preventing misinterpretation of unused slots.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 29 Oct 2026, 01:00 UTC

Technical details

References

Community reviews

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