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CVE-2021-47412 is a Linux kernel block-layer vulnerability caused by invoking request-queue quality-of-service completion callbacks for untracked block I/O operations. The rq_qos framework applies to request-based drivers, but bio_endio() can invoke rq_qos_done_bio() for bio-based drivers or untracked bios completed through error handling. In these cases, a request-queue reference may not be held, and the queue or its rq_qos state may already have been freed. Accessing this state during completion can cause a use-after-free and kernel panic.
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No public exploit code observed for this vulnerability.
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Linux kernel block-layer request QoS handling flaw.
A Linux kernel block-layer vulnerability involving invocation of rq_qos_ops->done_bio for a bio that is not tracked. The issue was resolved upstream and is classified as medium severity in the referenced Red Hat tracking record.
A Linux kernel block I/O flaw can cause use-after-free when rq_qos_ops->done_bio is called for an untracked bio and a freed request queue is accessed. This can trigger kernel panic and system crashes. Red Hat rates the vulnerability Moderate, with CVSS 3.1 score 4.7, requiring local access, low privileges, and high attack complexity; its assessment identifies availability impact but no confidentiality or integrity impact. Red Hat Enterprise Linux 8 kernel and kernel-rt fixes were issued on September 24, 2024, through RHSA-2024:7000 and RHSA-2024:7001, respectively. The listed RHEL 6, 7, and 9 components are marked not affected.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.