VulnerabilityPublished 13 Nov 2026

CVE-2026-128088: Eugeny russh · Time-of-check Time-of-use (TOCTOU) Race Condition

Affects Eugeny russhSource CVE Database V5

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Mentioned vulnerabilities

CVE-2026-116794

Not known to be exploited · CVSS 2.2 Low : upgrade to 0.65.1 when convenient.

Data as of 13 Nov 2026, 19:19 UTC

CVSS 3.1 base score

2.2Low

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	2.2

Patch: Available – fixed in 0.65.1

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

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

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
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: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on 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 13 Nov 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 13 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 Eugeny russh to 0.65.1.

Affected software

Product	Affected	Fixed in
Eugenyrussh	Affected >=0.65.0 <0.65.1	Fixed in 0.65.1

AI-suggested

Upgrade russh to version 0.65.1 or later, where this TOCTOU race condition vulnerability is fixed. No other mitigation is required as the fix addresses the issue directly.

Description

CVE-2026-128088 is a time-of-check to time-of-use (TOCTOU) race condition vulnerability in the Eugeny russh Rust SSH client and server library. The flaw exists in versions >=0.65.0 and <0.65.1 where the try_sign() function captures a private key reference before awaiting a confirmation step but does not revalidate the lock state afterward. This allows a remote SSH server using agent forwarding to bypass the current lock state during a signature request. The issue is fixed in version 0.65.1.

Impact

The vulnerability allows a remote SSH server using agent forwarding to bypass the agent's lock state during a pending signature request, potentially enabling unauthorized signature operations. However, private key material is not disclosed, and new requests after locking are rejected. The CVSS score of 2.2 reflects a low severity impact with limited integrity impact and no confidentiality or availability impact.

Summary

The vulnerability in russh arises from a TOCTOU race condition in the try_sign() method, which captures an Arc<PrivateKey> before awaiting Agent::confirm() and fails to revalidate the shared lock state or key presence after the await. Consequently, a remote peer can initiate a signature request while the agent is unlocked and receive the signature even if the agent is subsequently locked by another connection. Although new post-lock requests are rejected and private key material is not disclosed, the pending operation bypasses the lock state, representing a residual defect following remediation of a previous CVE (CVE-2026-116794). The flaw affects russh versions >=0.65.0 and <0.65.1 and is resolved in version 0.65.1.

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
Implementation
The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
Implementation
When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
Architecture and Design
Limit the interleaving of operations on files from multiple processes.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.3 (opens in a new tab)
V11.1.6 (opens in a new tab)
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Race Conditions via Symbolic Links (opens in a new tab)
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-863Incorrect Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #17OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Nov 2026, 19:19 UTC

WeaknessesCWE-367, CWE-863

Technical details

References

Community reviews

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