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Linux Kernel TIPC MSG_CRYPTO Heap Overflow
CVE-2021-43267 is a heap-based buffer overflow in the Linux kernel Transparent Inter-Process Communication (TIPC) module's handling of MSG_CRYPTO messages, specifically in tipc_crypto_key_rcv(). The vulnerable logic allocates a buffer based on the declared message payload size, then reads an attacker-controlled key length and copies algorithm-name and key data before confirming that the effective key structure fits within the allocation. An attacker can declare a small payload to obtain a small heap allocation and supply a larger key length, causing an overflow of attacker-controlled data.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation can yield Linux kernel privileges and result in complete compromise of an affected system. The heap overflow is reachable remotely when TIPC is exposed through a UDP bearer, and may also be reachable locally where an unprivileged user can configure TIPC.
If you can’t patch tonight, do this now.
Disable or unload the TIPC kernel module on systems that do not require TIPC. Avoid exposing TIPC via a UDP bearer on attacker-reachable networks; UDP TIPC listens for incoming messages on port 6118 when configured.
Patch, then assume compromise.
Install a Linux kernel update or distribution-provided kernel package containing the fix for CVE-2021-43267. The upstream fix performs MSG_CRYPTO size validation before copying attacker-controlled data and adds minimum packet-size, exact size-consistency, and maximum key-size checks. Kernel versions before 5.14.16 are affected according to the vulnerability description.
No validated public exploits yet. Hidden: 1 not loaded here.
6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.