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CVE-2025-40257 is a Linux kernel vulnerability in the Multipath TCP (MPTCP) subsystem caused by a race condition in mptcp_pm_del_add_timer(). The vulnerable path can invoke sk_stop_timer_sync() on an add-address timer associated with an entry that has already been freed by another execution context, resulting in a slab use-after-free during timer deletion. The fault was observed by syzbot as a KASAN-detected use-after-free in __timer_delete_sync(), with the call path traversing MPTCP packet option processing and MPTCP worker logic. The upstream fix adds RCU protection around the affected access pattern and also clarifies the logic by renaming a confusing timer-control variable.
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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.
8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux kernel MPTCP race condition/use-after-free vulnerability in mptcp_pm_del_add_timer() that can lead to slab-use-after-free, fixed by adding RCU protection.
Linux kernel MPTCP vulnerability that may allow privilege escalation or denial of service via a use-after-free in timer handling.
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.