CVE-2026-111062
Description
A flaw was found in russh. The SSH server fails to verify that the cryptographic signature algorithm in a public-key authentication payload matches the algorithm named in the authentication request. An authenticated remote client can exploit this flaw by claiming an approved algorithm while submitting a signature generated using a restricted or deprecated algorithm. This allows the client to bypass server cryptographic restrictions or cause the server to record misleading authentication audit logs.
Statement
This vulnerability is rated as having a Low severity impact because exploitation still requires an attacker to possess an authorized private key, preventing unauthorized access. The flaw allows an authenticated client to supply a valid signature using a weaker algorithm than announced, potentially evading cryptographic policy restrictions or misrepresenting algorithm choices in server audit logs. Only server deployments that enforce specific signature algorithms or rely on requested algorithms for compliance logging are impacted, while client-side usage is unaffected.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.1 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | High | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | Low | N/A | N/A |
| Availability Impact | None | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
Understanding the Weakness (CWE)
Access Control,Integrity,Confidentiality
Technical Impact: Gain Privileges or Assume Identity; Modify Application Data; Execute Unauthorized Code or Commands
An attacker could gain access to sensitive data and possibly execute unauthorized code.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
