[Go v1.20] CVE-2025-22869: ssh: limit the size of the internal packet queue while waiting for KEX#1
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germanparente merged 1 commit intoJul 7, 2026
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In the SSH protocol, clients and servers execute the key exchange to generate one-time session keys used for encryption and authentication. The key exchange is performed initially after the connection is established and then periodically after a configurable amount of data. While a key exchange is in progress, we add the received packets to an internal queue until we receive SSH_MSG_KEXINIT from the other side. This can result in high memory usage if the other party is slow to respond to the SSH_MSG_KEXINIT packet, or memory exhaustion if a malicious client never responds to an SSH_MSG_KEXINIT packet during a large file transfer. We now limit the internal queue to 64 packets: this means 2MB with the typical 32KB packet size. When the internal queue is full we block further writes until the pending key exchange is completed or there is a read or write error. Thanks to Yuichi Watanabe for reporting this issue. Change-Id: I1ce2214cc16e08b838d4bc346c74c72addafaeec Reviewed-on: https://go-review.googlesource.com/c/crypto/+/652135 Reviewed-by: Neal Patel <nealpatel@google.com> Auto-Submit: Gopher Robot <gobot@golang.org> Reviewed-by: Roland Shoemaker <roland@golang.org> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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CVE.patch