Medium severity · published Sep 29, 2026
CVE-2026-102821
Russh: Unbounded memory exhaustion via CHANNEL_OPEN flood during a client-stalled rekey
6.5
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 29% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RU
russh · Eugeny
< 0.63.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-102821
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-102821
x_refsource_CONFIRM
https://github.com/Eugeny/russh/security/advisories/GHSA-35g8-35p8-c8fw
x_refsource_MISC
https://github.com/Eugeny/russh/commit/a282af361ac99bc76b80876d1aae128e89dbf66b
x_refsource_MISC
https://github.com/Eugeny/russh/releases/tag/v0.63.2
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