How severe is CVE-2026-18654?

No CVSS score has been assigned to CVE-2026-18654 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-18654?

CVE-2026-18654 affects the following packages: awscli (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-18654?

Update awscli to 1.45.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-18654 is resolved across your whole dependency graph.

How do I detect CVE-2026-18654 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for awscli, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-18654 if there is no patch (or I can't update yet)?

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.

Is CVE-2026-18654 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-18654 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-18654?

CVE-2026-18654 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 40th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-18654?

CVE-2026-18654 is classified as CWE-322 (CWE-322). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-18654 published, and has it been updated?

CVE-2026-18654 was published on August 3, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-18654 — awscli

CVE-2026-18654 is a CWE-322 vulnerability in awscli. A fix is available for awscli — see the affected versions and patch details below.

Disabled SSH host key verification in Amazon AWS CLI EMR helper commands

Also known asGHSA-hqvf-45jj-mccqPYSEC-2026-3627

Published

Aug 3, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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-2026-18654.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk+0.17%

Lower risk than most CVEs40th percentile — riskier than 40% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍awscli

Real-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

The AWS Command Line Interface (AWS CLI) is a unified tool to manage AWS services from the command line. An issue exists where the EMR SSH helper commands (aws emr ssh, aws emr socks, aws emr put, aws emr get) passed StrictHostKeyChecking=no to the underlying SSH client, disabling host key verification.

Impact

A network-positioned actor could perform a man-in-the-middle action to intercept SSH sessions and file transfers between the client and EMR cluster instances. Successful exploitation requires the actor to have network access on the path between the client machine and the EMR cluster endpoint. This could result in full visibility of commands executed, files transferred, and credentials passed over the SSH session.

Impacted versions: AWS CLI v1 <= 1.45.27, AWS CLI v2 <= 2.35.2

Patches

This issue has been addressed in AWS CLI v1 version 1.45.28 and AWS CLI v2 version 2.35.3. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.

Workarounds

There is no workaround. The insecure SSH option was hardcoded and could not be overridden by the user.

References

If you have any questions or comments about this advisory, we ask that you contact AWS Security via our vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.

Acknowledgement

We would like to thank Ali Sunbul for collaborating on this issue through the coordinated vulnerability disclosure process.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`awscli`	all versions	1.45.28`pip install --upgrade 'awscli==1.45.28'`

Affected Products

1 product · 2 configurations

Application

aws command line interfaceamazon

≥ 2.0.0 && < 2.35.3

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for awscli, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update awscli to 1.45.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-18654 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.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

The AWS CLI disables SSH host key verification (StrictHostKeyChecking=no) when running the `aws emr ssh`, `aws emr socks`, `aws emr put`, and `aws emr get` subcommands against an Amazon EMR cluster. An attacker holding a machine-in-the-middle position on the network path between the client and the EMR node can…

Workaround published by Red Hat

Users who do not run the `aws emr ssh`, `aws emr socks`, `aws emr put`, or `aws emr get` subcommands are not exposed. Where these subcommands are required, verify the EMR node's SSH host key out-of-band before connecting, or restrict their use to trusted networks where a machine-in-the-middle attacker cannot intercept traffic. Upgrading to awscli 1.45.28 or later (v1 line) or awscli2 2.35.3 or later (v2 line) removes the vulnerable behavior.

Source: Red Hat security advisory for CVE-2026-18654 (CC BY 4.0)

Frequently Asked Questions

### Summary The AWS Command Line Interface (AWS CLI) is a unified tool to manage AWS services from the command line. An issue exists where the EMR SSH helper commands (`aws emr ssh`, `aws emr socks`, `aws emr put`, `aws emr get`) passed `StrictHostKeyChecking=no` to the underlying SSH client, disabling host key verification. ### Impact A network-positioned actor could perform a man-in-the-middle action to intercept SSH sessions and file transfers between the client and EMR cluster instances. Successful exploitation requires the actor to have network access on the path between the client machi

O3 Security · Impact-Aware SCA

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