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CVE-2025-40257 is a use-after-free vulnerability in the Linux kernel Multipath TCP (MPTCP) path manager. A race in mptcp_pm_del_add_timer() allows sk_stop_timer_sync() to access an address-announcement entry's timer after another execution context has freed the entry. The failure was detected by syzbot as a KASAN slab-use-after-free in __timer_delete_sync(), involving a four-byte invalid read in kernel worker context. The vulnerability can potentially cause denial of service or privilege escalation. The fix adds read-copy-update (RCU) protection around the affected operation.
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A race condition in the Linux kernel's Multipath TCP (MPTCP) implementation can cause a slab use-after-free when timer cleanup accesses an already-freed entry. The fix adds RCU protection. The advisory rates the vulnerability critical, with a CVSS v3 base score of 9.8, and recommends updating the Echo linux package and related packages to version 6.1.159-1 or later. It explicitly states that no known exploits are available.
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.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.