CVE-2026-91987: atomic-agents-stack before 1.1.0 Cost Guardrail Bypass via Unknown Model

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-15 · updated 2026-09-24
Weakness: CWE-770

Description

atomic-agents-stack before 1.1.0 contains a cost-guardrail bypass in the _estimate_batch_cost function that returns zero cost for unknown models not in the pricing table. Attackers can configure deployments with unknown model identifiers to bypass daily cost caps and exceed budget limits in parallel batch operations.

Affected products

dep0we atomic-agents-stack: before 1.1.0 — fixed in 1.1.0

How to fix

Upgrade to a fixed version: dep0we atomic-agents-stack 1.1.0. Check the vendor advisory for mitigations.

References

https://github.com/dep0we/atomic-agents-stack/security/advisories/GHSA-j659-8xh6-5pq5
https://www.vulncheck.com/advisories/atomic-agents-stack-before-1.1.0-cost-guardrail-bypass-via-unknown-model

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