CVE-2025-39946

moderate-risk
Published 2025-10-04

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.

Do I need to act?

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0.02% chance of exploitation
EPSS score — low exploit probability
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
+
Fix available
Upgrade to: b36462146d86b1f22e594fe4dae611dffacfb203, 4cefe5be73886f383639fe0850bb72d5b568a7b9, 208640e6225cc929a05adbf79d1df558add3e231, 61ca2da5fb8f433ce8bbd1657c84a86272133e6b, 0aeb54ac4cd5cf8f60131b4d9ec0b6dc9c27b20d
9
CVSS 9.8/10 Critical
NETWORK / LOW complexity

Affected Vendors

46
/ 100
moderate-risk
Severity 32/34 · Critical
Exploitability 0/34 · Minimal
Exposure 14/34 · Moderate