What’s Vulnerable › Vulnerabilities

CVE-2026-102821: Russh: Unbounded memory exhaustion via CHANNEL_OPEN flood during a client-stalled rekey

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-29 · updated 2026-09-30
• Weakness: CWE-400

Description

Russh is a Rust SSH client and server library. Prior to 0.63.2, an authenticated remote peer can send SSH_MSG_KEXINIT without the required SSH_MSG_KEX_ECDH_INIT and then flood SSH_MSG_CHANNEL_OPEN messages while SessionKexState::InProgress prevents priority_receiver in russh/src/server/session.rs from being drained. The server continues processing network input and enqueues a ChannelOpenReply for each request on an unbounded channel, allowing one connection to grow memory until the process is terminated. This issue is fixed in version 0.63.2.

Affected products

• Eugeny russh: before 0.63.2

References

• https://github.com/Eugeny/russh/commit/a282af361ac99bc76b80876d1aae128e89dbf66b
• https://github.com/Eugeny/russh/releases/tag/v0.63.2
• https://github.com/Eugeny/russh/security/advisories/GHSA-35g8-35p8-c8fw
• https://github.com/Eugeny/russh/security/advisories/GHSA-35g8-35p8-c8fw

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