VulnerabilityPublished 30 Sep 2026Updated 12 Nov 2026

CVE-2026-102823: Russh · Client `Handler` callbacks run for channels the client never opened

Affects russhSource GCVE Database

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Authoritative record:CVE-2026-102823· High 7.5

Not known to be exploited · CVSS 7.5 High : upgrade to 0.63.1 soon.

Data as of 12 Nov 2026, 08:07 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 0.63.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 29 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade russh to 0.63.1.

Affected software

Product	Affected	Fixed in
crates.iorussh`pkg:cargo/russh`Other threats	Affected >=0.0.0-0 <0.63.1	Fixed in 0.63.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade russh to version 0.63.1 or later, where the client properly verifies channel numbers before invoking client::Handler callbacks. This fix prevents processing of messages for channels that are not established and confirmed. No additional mitigation is required once the client is updated.

Description

The russh client improperly processes channel messages from an SSH server without verifying that the channel number belongs to a channel the client opened and the server confirmed. This allows a malicious or compromised SSH server to send messages for arbitrary channel numbers, potentially causing the client application to record incorrect channel states or panic. The issue is fixed in russh version 0.63.1, which adds proper checks to ignore messages for unestablished channels.

Impact

A malicious or compromised SSH server can exploit this vulnerability to send forged channel messages to the russh client, causing the client application to misinterpret channel states. This can lead to incorrect recording of exit statuses, premature channel closure events, or application panics due to referencing unknown channels. The impact affects the integrity of client-side channel state handling but does not affect confidentiality or availability directly.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Nov 2026, 08:07 UTC

Technical details

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