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Critical severity9.8NVD Advisory· Published Oct 4, 2025· Updated Apr 6, 2026

CVE-2025-39946

CVE-2025-39946

Description

In the Linux kernel, the following vulnerability has been resolved:

tls: make sure to abort the stream if headers are bogus

Normally we wait for the socket to buffer up the whole record before we service it. If the socket has a tiny buffer, however, we read out the data sooner, to prevent connection stalls. Make sure that we abort the connection when we find out late that the record is actually invalid. Retrying the parsing is fine in itself but since we copy some more data each time before we parse we can overflow the allocated skb space.

Constructing a scenario in which we're under pressure without enough data in the socket to parse the length upfront is quite hard. syzbot figured out a way to do this by serving us the header in small OOB sends, and then filling in the recvbuf with a large normal send.

Make sure that tls_rx_msg_size() aborts strp, if we reach an invalid record there's really no way to recover.

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Affected products

118

Patches

Vulnerability mechanics

References

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