CVE-2026-86121: Missing Auth (CVSS 9.8)

Description

Cua computer-server versions before 0.3.42 skip authentication when the CONTAINER_NAME environment variable is unset and bind to all interfaces by default, allowing unauthenticated attackers to execute arbitrary commands. Attackers can reach TCP port 8000 to run shell commands via the run_command endpoint, read and write arbitrary files through file operation endpoints, and access interactive PTY shells without authentication.

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CVSS v3.1 Score

9.8

CRITICAL

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

EPSS — Exploit Prediction

0.0059

Probability of exploitation

0.47%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-306 Missing Authentication

References

Other References

https://github.com/trycua/cua https://github.com/trycua/cua/blob/10a2e71792db/libs/python/computer-server/computer_server/cli.py https://github.com/trycua/cua/blob/10a2e71792db/libs/python/computer-server/computer_server/main.py https://github.com/trycua/cua/commit/59cf25c0ec54 https://github.com/trycua/cua/issues/1892 https://www.vulncheck.com/advisories/cua-computer-server-before-0.3.42-unauthenticated-rce-via-desktop-control https://github.com/trycua/cua/issues/1892

Frequently Asked Questions

What is CVE-2026-86121? +

Cua computer-server versions before 0.3.42 skip authentication when the CONTAINER_NAME environment variable is unset and bind to all interfaces by default, allowing unauthenticated attackers to execute arbitrary commands. Attackers can reach TCP port 8000 to run shell commands via the run_command endpoint, read and write arbitrary files through file operation endpoints, and access interactive PTY shells without authentication. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-86121? +

CVE-2026-86121 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0059, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-86121? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-86121