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CVE-2021-47321 is a use-after-free vulnerability in Linux kernel watchdog drivers. During driver removal, affected drivers used del_timer(), which cancels a timer but does not wait for an already executing timer callback to complete. The callback could consequently continue after driver removal and dereference memory that had been freed. The upstream fix replaces del_timer() with del_timer_sync(), which waits for the timer handler to finish and prevents it from rescheduling itself.
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Potential use-after-free vulnerability in the Linux kernel watchdog subsystem caused by unsafe timer handling.
Linux kernel watchdog use-after-free flaw.
A Linux kernel watchdog subsystem use-after-free vulnerability, resolved by calling del_timer_sync() to safely synchronize timer deletion.
A use-after-free vulnerability (CWE-416) in the Linux kernel watchdog driver caused by use of del_timer() rather than waiting for an active timer handler to complete. It can cause system instability or crashes; Red Hat rates its impact as Moderate (CVSS 4.4) for its products.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.