THREATPORT/VULNERABILITY/CVE-2025-39946
CRITICAL SEVERITY

CVE-2025-39946

Linux Kernel vulnerability

CVSS
9.8
EPSS
8.9%
EPSS pct
95th
Exploited
No known
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.
Affected vendor
Linux
Affected product
Linux Kernel
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2025-10-04

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to confidentiality, high impact to integrity, high impact to availability.

Its EPSS score of 8.9% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 95% of all scored CVEs.

Check your external exposure to CVE-2025-39946

  • Confirm whether Linux Linux Kernel is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2025-39946.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2025-39946

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