CVE-2024-39920

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-07-03 · updated 2026-06-17
Weakness: CWE-1255

Description

The TCP protocol in RFC 9293 has a timing side channel that makes it easier for remote attackers to infer the content of one TCP connection from a client system (to any server), when that client system is concurrently obtaining TCP data at a slow rate from an attacker-controlled server, aka the "SnailLoad" issue. For example, the attack can begin by measuring RTTs via the TCP segments whose role is to provide an ACK control bit and an Acknowledgment Number.

Affected products

IETF Tcp: 9293

References

https://github.com/IAIK/SnailLoad
https://news.ycombinator.com/item?id=40809629
https://twitter.com/tugraz/status/1805272833322299412
https://www.instagram.com/p/C8wpO1UtExw/
https://www.rfc-editor.org/rfc/rfc9293.txt
https://www.snailload.com
https://www.snailload.com/snailload.pdf
https://www.tugraz.at/en/tu-graz/services/news-stories/tu-graz-news/singleview/article/neue-sicherheitsluecke-erlaubt-ueberwachung-besuchter-websites-und-angesehener-videos
https://github.com/IAIK/SnailLoad
https://news.ycombinator.com/item?id=40809629
https://twitter.com/tugraz/status/1805272833322299412
https://www.instagram.com/p/C8wpO1UtExw/

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