CVE-2026-108711: Auth Bypass (CVSS 4.3)

Description

Plastic Labs Honcho through 3.3.0 contains an incorrect authorization vulnerability that allows peer- or session-scoped API key holders to read workspace data because get_or_create_workspace checks only the workspace claim. Attackers can submit their parent workspace name to the POST /v3/workspaces endpoint to retrieve workspace metadata and configuration, including custom_instructions, reserved for workspace or admin keys.

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CVSS v3.1 Score

4.3

MEDIUM

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

EPSS — Exploit Prediction

0.0028

Probability of exploitation

0.19%

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-863 Incorrect Authorization

References

Other References

https://github.com/plastic-labs/honcho https://github.com/plastic-labs/honcho/blob/608aec8a928da13c540262ed980c569448fb53ab/src/crud/workspace.py#L112-L119 https://github.com/plastic-labs/honcho/blob/608aec8a928da13c540262ed980c569448fb53ab/src/routers/workspaces.py#L41-L72 https://github.com/plastic-labs/honcho/blob/608aec8a928da13c540262ed980c569448fb53ab/src/security.py#L218-L225 https://hackmd.io/@haind/honcho-scoped-jwt-workspace-config-disclosure https://www.vulncheck.com/advisories/plastic-labs-honcho-through-3.3.0-incorrect-authorization-via-post-v3-workspaces

Frequently Asked Questions

What is CVE-2026-108711? +

Plastic Labs Honcho through 3.3.0 contains an incorrect authorization vulnerability that allows peer- or session-scoped API key holders to read workspace data because get_or_create_workspace checks only the workspace claim. Attackers can submit their parent workspace name to the POST /v3/workspaces endpoint to retrieve workspace metadata and configuration, including custom_instructions, reserved for workspace or admin keys. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-108711? +

CVE-2026-108711 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0028, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-108711? +

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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