I/O hang via stale scheduler flags
Published Oct 18, 2026 · Updated Oct 18, 2026
Request reuse in Linux blk-mq allows attackers to hang block I/O queues when cached requests retain passthrough scheduler flags. In block/blk-mq.c, requests allocated for passthrough operations retain a cleared RQF_USE_SCHED flag when reused for reads or writes, skipping scheduler preparation and completion callbacks. With Kyber scheduling, the missing completion callback leaks domain tokens and stalls the affected queue; required attacker privileges and a network trigger are not documented.
Summary
What happened
Request reuse in Linux blk-mq allows attackers to hang block I/O queues when cached requests retain passthrough scheduler flags. In block/blk-mq.c, requests allocated for passthrough operations retain a cleared RQF_USE_SCHED flag when reused for reads or writes, skipping scheduler preparation and completion callbacks. With Kyber scheduling, the missing completion callback leaks domain tokens and stalls the affected queue; required attacker privileges and a network trigger are not documented.
The record
- CVE
- CVE-2026-98820
- Published
- Oct 18, 2026
- Updated
- Oct 18, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1499.004
- Attack vector
- Unavailable
- Privileges
- Unavailable
Timeline
How it unfolded
- Oct 18, 2026CVE publishedPublication date reported by the CVE source.
- Oct 18, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=4b6a5d9cea911424e84107df8c4eb8317938d2cd <2c47ebc27fa72078e26177cd458cdaf3006a9685
- Affected versionversion=4b6a5d9cea911424e84107df8c4eb8317938d2cd <790730e4d95de8356a573d4b4864486bba731863
- Affected versionversion=4b6a5d9cea911424e84107df8c4eb8317938d2cd <ab6c756f28c741d704a7c3e04814bfc3adf6f818
- Affected versionversion=6.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
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Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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