CVE-2026-54548: Kas Kas Persistently Disables SSH Host Vulnerability

LOW
Advisory Identifier: GHSA-mv8m-v9v6-5f94
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CVSS 3.3
CWE-295
Published
Advisory Summary

CVE-2026-54548 is a LOW (CVSS 3.3) kas persistently disables ssh host vulnerability (CWE-295: Improper Certificate Validation) affecting Kas libraries in the PyPI ecosystem. The issue involves kas persistently disables ssh host key checking. Remediation is available by upgrading affected packages to version 5.4.

CVE-2026-54548 at a Glance

CVE Identifier CVE-2026-54548
GHSA Identifier GHSA-mv8m-v9v6-5f94
Severity LOW
CVSS v3.1 Base Score 3.3
CWE Classification CWE-295: Improper Certificate Validation
Affected Product Kas
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 3.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N).

Attack Vector Local (AV:L)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-54548

To remediate this vulnerability, upgrade all affected Kas dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

kas fixed: 5.4 
pip install kas>=5.4
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show kas

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-54548, inspect your installed packages using pip:

pip show kas

Analyze the terminal output to locate any version of Kas in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.4), your application is affected.

Note: The pip show kas command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-295: Improper Certificate Validation, where the product does not validate, or incorrectly validates, a certificate. In Kas, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary kas persistently disables SSH host key checking for the invoking user when internal SSH key setup is triggered via `SSH_PRIVATE_KEY` or `SSH_PRIVATE_KEY_FILE` and no user-specific SSH configuration file exists so far. When this path is used, kas creates `~/.ssh/config` with a global `Host *` rule containing `StrictHostKeyChecking no`. This was intended to ease the use of kas in short-lived CI environments that lack a pre-configured set of known hosts. In case a local user had no SSH configuration file so far, this approach weakens SSH host authenticity verification beyond the lifetime and scope of the kas command, increasing the risk of successful man-in-the-middle attacks against future SSH connections made by the same user. ### Patches Such SSH configurations were created since the very first public release. The issue is addressed now by commit <FILLME> which is part of kas version 5.4. ### Workarounds Since kas 2.6.3, a local user's SSH configuration is only written if it didn't exist before. From that version on, the issue can be avoided by creating an own `~/.ssh/config` prior to calling kas. If kas was already called, `~/.ssh/config` should be inspected and undesired settings created by kas should be removed.

CVE-2026-54548 Affected Kas Versions

1 component(s)
Fixed Versions:
5.4
Product / Package Ecosystem Affected Versions Fixed Version
kas
pypi/kas
PyPI
< 5.4
5.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/siemens/kas/security/advisories/GHSA-mv8m-v9v6-5f94
Security Fix Commit FIX COMMIT
https://github.com/siemens/kas/commit/1c1e861c9f241ce082b86bef6bedc7da9b676294
Kas Source Repository REPOSITORY
https://github.com/siemens/kas
Kas Release RELEASE
https://github.com/siemens/kas/releases/tag/5.4

Frequently Asked Questions

What is CVE-2026-54548?
CVE-2026-54548 is a security vulnerability in Kas involving kas Persistently Disables SSH Host Key Checking under CWE-295: Improper Certificate Validation.
Which Kas versions are affected?
Affected versions include releases prior to 5.4 across affected packages: kas.
What version fixes CVE-2026-54548?
Upgrading to 5.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is kas affected?
Yes, kas is affected in releases prior to 5.4. Upgrade your dependency to 5.4 or later.
What is the CVSS score of CVE-2026-54548?
CVE-2026-54548 has a CVSS v3.1 base score of 3.3 (LOW) with vector string CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2026-54548?
CVE-2026-54548 is classified under CWE-295: Improper Certificate Validation (The product does not validate, or incorrectly validates, a certificate.).
How can I check PyPI dependencies for CVE-2026-54548?
Run the dependency tree command: 'pip show kas'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mv8m-v9v6-5f94",
  "modified" : "2026-08-26T14:18:24Z",
  "published" : "2026-08-26T14:18:24Z",
  "aliases" : [ "CVE-2026-54548" ],
  "summary" : "kas Persistently Disables SSH Host Key Checking",
  "details" : "### Summary\n\nkas persistently disables SSH host key checking for the invoking user when internal SSH key setup is triggered via `SSH_PRIVATE_KEY` or `SSH_PRIVATE_KEY_FILE` and no user-specific SSH configuration file exists so far.\n\nWhen this path is used, kas creates `~/.ssh/config` with a global `Host *` rule containing `StrictHostKeyChecking no`. This was intended to ease the use of kas in short-lived CI environments that lack a pre-configured set of known hosts. In case a local user had no SSH configuration file so far, this approach weakens SSH host authenticity verification beyond the lifetime and scope of the kas command, increasing the risk of successful man-in-the-middle attacks against future SSH connections made by the same user.\n\n### Patches\n\nSuch SSH configurations were created since the very first public release. The issue is addressed now by commit <FILLME> which is part of kas version 5.4.\n\n### Workarounds\n\nSince kas 2.6.3, a local user's SSH configuration is only written if it didn't exist before. From that version on, the issue can be avoided by creating an own `~/.ssh/config` prior to calling kas. If kas was already called, `~/.ssh/config` should be inspected and undesired settings created by kas should be removed.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "kas"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/siemens/kas/security/advisories/GHSA-mv8m-v9v6-5f94"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/siemens/kas/commit/1c1e861c9f241ce082b86bef6bedc7da9b676294"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/siemens/kas"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/siemens/kas/releases/tag/5.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-295" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-26T14:18:24Z",
    "nvd_published_at" : null
  }
}