VulnerabilityPublished 18 Oct 2026

CVE-2026-98789: Linux kernel · bpf: Fix objects stuck in free_by_rcu_ttrace

Affects Linux kernelSource CVE Database V5

Not known to be exploited : upgrade to fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043 or 33d0a5d2fee06a51f2f056dd901296515912e954 when convenient.

Data as of 26 Oct 2026, 10:12 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 4% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043, 33d0a5d2fee06a51f2f056dd901296515912e954

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 fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043 or 33d0a5d2fee06a51f2f056dd901296515912e954.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 8d5a8011b35d387c490a5c977b1d9eb4798aa071, < fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043	Fixed in fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043
LinuxLinux	Affected ≥ 8d5a8011b35d387c490a5c977b1d9eb4798aa071, < 33d0a5d2fee06a51f2f056dd901296515912e954	Fixed in 33d0a5d2fee06a51f2f056dd901296515912e954
LinuxLinux	Affected =6.1	Fixed in–
Debiandebian/linux`pkg:deb/debian/linux`Other threats	Affected =6.1	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 and has been applied in the Linux kernel commits fbd97dd1d3ce32d32fb7be86acc3fdb7c04fa043 and 33d0a5d2fee06a51f2f056dd901296515912e954. Users and administrators should update to these fixed versions or later to remediate this issue.

Description

A vulnerability in the Linux kernel related to BPF memory object freeing has been fixed. The issue involved objects getting stuck in the free_by_rcu_ttrace state due to improper handling of the call_rcu_ttrace_in_progress flag, potentially causing unbounded accumulation of such objects. The fix introduces a three-state mechanism for call_rcu_ttrace_in_progress and changes the queuing behavior of __free_rcu() to ensure proper freeing of these objects.

Impact

The vulnerability can cause unbounded accumulation of BPF memory objects stuck in the free_by_rcu_ttrace state, potentially leading to increased memory usage and resource exhaustion in the kernel. This could degrade system performance or stability over time, especially under workloads that create and destroy many BPF maps or objects.

Summary

The Linux kernel vulnerability CVE-2026-98789 concerns the BPF subsystem where objects remain stuck in the free_by_rcu_ttrace list because do_call_rcu_ttrace() returns early when call_rcu_ttrace_in_progress is set. This leaves objects unreleased until free_bulk() or alloc_bulk() is called again for the same bpf_mem_cache, which may never occur, causing unbounded memory retention. The fix changes call_rcu_ttrace_in_progress to a three-state flag to better track freeing progress and modifies __free_rcu() to queue itself properly under rcu_read_lock(), ensuring that objects are freed timely and preventing resource buildup.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 09:57 UTC

Technical details

References

Community reviews

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