CVE-2025-21710

Technical Description

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

tcp: correct handling of extreme memory squeeze

Testing with iperf3 using the "pasta" protocol splicer has revealed

a problem in the way tcp handles window advertising in extreme memory

squeeze situations.

Under memory pressure, a socket endpoint may temporarily advertise

a zero-sized window, but this is not stored as part of the socket data.

The reasoning behind this is that it is considered a temporary setting

which shouldn't influence any further calculations.

However, if we happen to stall at an unfortunate value of the current

window size, the algorithm selecting a new value will consistently fail

to advertise a non-zero window once we have freed up enough memory.

This means that this side's notion of the current window size is

different from the one last advertised to the peer, causing the latter

to not send any data to resolve the sitution.

The problem occurs on the iperf3 server side, and the socket in que

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References