CVE-2026-54548 is a low-severity (CVSS 3.3) CWE-295 vulnerability in kas. A fix is available for kas — see the affected versions and patch details below.
kas: Persistent SSH Host Key Checking Disablement
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54548.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-54548 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
kasReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | kas | all versions | 5.4pip install --upgrade 'kas==5.4' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for kas, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update kas to 5.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54548 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-54548 in your dependencies?
Find it across PyPI, including transitive dependencies.