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CVE-2021-47356 is a use-after-free vulnerability in the Linux kernel mISDN subsystem's HFC_cleanup() removal path. The cleanup routine used del_timer(), which cancels a timer without waiting for an already executing timer callback to complete. Consequently, the driver resources can be released while the timer handler is still executing; the handler may then access freed memory or reschedule itself. The upstream fix replaces del_timer() with del_timer_sync(), ensuring that the callback has completed and cannot reschedule before cleanup proceeds.
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What an attacker gets, and what they’ve been doing with it.
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No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Potential use-after-free vulnerability in the Linux kernel mISDN HFC_cleanup() function.
Possible use-after-free in the Linux mISDN HFC cleanup routine.
A possible use-after-free flaw in the Linux kernel mISDN HFC cleanup routine.
Linux kernel mISDN HFC cleanup use-after-free vulnerability.
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.