Linux Kernel up to 7.1.5/7.2-rc3 xfrm net/xfrm/xfrm_state.c xfrm_user_policy double free

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.1.5/7.2-rc3. It has been rated as very critical. This affects the function xfrm_user_policy of the file net/xfrm/xfrm_state.c of the component xfrm. The manipulation leads to double free. This vulnerability is documented as CVE-2026-64581. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.1.5/7.2-rc3 and classified as very critical. This issue affects the function xfrm_user_policy of the file net/xfrm/xfrm_state.c of the component xfrm. The manipulation with an unknown input leads to a double free vulnerability. Using CWE to declare the problem leads to CWE-415. The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: xfrm: fix sk_dst_cache double-free in xfrm_user_policy() xfrm_user_policy() clears the socket dst cache with __sk_dst_reset(), i.e. the non-atomic __sk_dst_set(sk, NULL): it reads sk_dst_cache with rcu_dereference_protected(), stores NULL and dst_release()s the old dst. That is only safe if no other thread modifies sk_dst_cache concurrently. For a connected UDP socket that does not hold: the transmit fast path (udp_sendmsg -> sk_dst_check -> sk_dst_reset) resets the cache locklessly with an atomic xchg(). A per-socket policy change racing a send can make both sides observe the same old dst and each dst_release() it, dropping the socket's single reference twice and freeing the xfrm_dst bundle while it is still referenced: BUG: KASAN: slab-use-after-free in dst_release Write of size 4 at addr ffff88801897b6c0 by task exploit/155 Call Trace: ... dst_release (... ./include/linux/rcuref.h:109) xfrm_user_policy (./include/net/sock.h:2239 ./include/net/sock.h:2256 net/xfrm/xfrm_state.c:3053) do_ip_setsockopt (net/ipv4/ip_sockglue.c:1347) ip_setsockopt (net/ipv4/ip_sockglue.c:1417) do_sock_setsockopt (net/socket.c:2368) __sys_setsockopt (net/socket.c:2393) __x64_sys_setsockopt (net/socket.c:2396) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Reachable by an unprivileged user via a user+network namespace. Use the atomic sk_dst_reset() so the cache is cleared and released with a single xchg(): whichever side wins releases the dst once, the other sees NULL and does nothing. Behaviour is otherwise unchanged.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-64581 since 07/19/2026. The exploitation is known to be easy. The attack may be initiated remotely. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 08/05/2026).

Upgrading to version 7.1.6 or 7.2-rc4 eliminates this vulnerability. Applying the patch 96b678d08268b5f5c6fc99d4289d9b7e334fc683/c283e9ada7fcb7dd4b10592623086b2e6d2f9925 is able to eliminate this problem.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-53275). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4
• 7.1.5
• 7.2-rc1
• 7.2-rc2
• 7.2-rc3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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