{"id":"CVE-2026-91987","aliases":["EUVD-2026-78658","GHSA-gpqc-jrqh-x9xp","GHSA-j659-8xh6-5pq5"],"status":"published","title":"atomic-agents-stack before 1.1.0 Cost Guardrail Bypass via Unknown Model","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.","severity":{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00476,"percentile":0.41458,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-770"],"published":"2026-08-17T21:50:01Z","modified":"2026-10-28T02:30:59Z","fixes":[{"ecosystem":"PyPI","package":"atomic-agents-stack","fixed_in":["1.1.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"atomic-agents-stack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.0.0"},{"fixed":"1.1.0"}]}]},{"source":"osv","ecosystem":"PyPI","package":"atomic-agents-stack","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.0"}]}],"versions":["1.0.0"]}],"products":[{"vendor":"dep0we","product":"atomic-agents-stack"}],"references":[{"url":"https://github.com/dep0we/atomic-agents-stack/security/advisories/GHSA-j659-8xh6-5pq5","tags":["vendor-advisory","advisory","web"]},{"url":"https://www.vulncheck.com/advisories/atomic-agents-stack-before-1.1.0-cost-guardrail-bypass-via-unknown-model","tags":["third-party-advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91987","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-gpqc-jrqh-x9xp"},{"url":"https://github.com/dep0we/atomic-agents-stack/releases#release-v1.1.0","tags":["web"]},{"url":"https://github.com/advisories/GHSA-j659-8xh6-5pq5"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91987.json","tags":["advisory"]},{"url":"https://github.com/dep0we/atomic-agents-stack","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-91987","title":"atomic-agents-stack before 1.1.0 Cost Guardrail Bypass via Unknown Model","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.","status":"published","published":"2026-09-15T15:18:29.633Z","modified":"2026-09-17T15:15:25.383Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high","assessor":"cna"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T14:19:52.773089Z"}],"euvd":[{"id":"EUVD-2026-78658","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.","status":"published","published":"2026-09-15T15:18:29Z","modified":"2026-09-17T15:15:25Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"}],"updated_at":"2026-11-02T17:28:11.615612Z"}],"ghsa":[{"id":"GHSA-gpqc-jrqh-x9xp","title":"atomic-agents-stack before 1.1.0 contains a cost-guardrail bypass in the _estimate_batch_cost...","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.","status":"published","published":"2026-09-15T18:32:31Z","modified":"2026-09-15T18:32:43Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T15:11:54.818367Z"},{"id":"GHSA-j659-8xh6-5pq5","title":"atomic-agents-stack: Parallel helper/delegate batch reserves $0 for models absent from the pricing table, bypassing the cost-cap fan-out guard","description":"`_estimate_batch_cost` (`atomic_agents/agent.py`) looks up the per-model output price with `PRICING.get(model, {})`, returning 0.0 for any model not in the hardcoded pricing table. `_check_batch_reservation` then early-returns when the reservation is \u003c= 0, skipping the batch reservation entirely. That reservation is the only defense against the documented fan-out race where every parallel helper/delegate reads the identical pre-batch on-disk cost total and each passes its individual check even though the collective spend overruns the configured cap.\n\n**Impact:** an operator running any model not in the pricing table (self-hosted/Ollama/vLLM, a new provider SKU) with `cost_guardrails` + `daily_cap_usd` set believes the cap protects them, but a single parallel batch can blow past the cap. The parallel-helper `model` argument can also be steered to an unknown id. The sibling `dream._estimate_dream_cost` does this correctly (`PRICING.get(model, _fallback_pricing())`), which makes this a clear defect.\n\n**Affected:** `agent.py` (`_estimate_batch_cost` / `_check_batch_reservation`), all versions through 1.0.0.\n\n**Fix:** use `PRICING.get(model, _costs._fallback_pricing())['output']` (mirror dream/calc_cost). Add a conformance test asserting an unknown-model batch reserves \u003e 0 and that an over-cap unknown-model batch raises `CostGuardrailBlocked`.","status":"published","published":"2026-08-17T21:50:01Z","modified":"2026-08-17T21:50:02Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T14:41:01.23108Z"}],"nvd":[{"id":"CVE-2026-91987","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.","status":"published","published":"2026-09-15T16:17:57.3Z","modified":"2026-09-24T20:48:01.433Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"secondary"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T14:12:47.668237Z"}],"osv":[{"id":"CVE-2026-91987","title":"atomic-agents-stack before 1.1.0 Cost Guardrail Bypass via Unknown Model","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.","status":"published","published":"2026-09-15T15:18:29.633Z","modified":"2026-10-28T02:30:59.857915533Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T15:45:20.269367Z"},{"id":"GHSA-j659-8xh6-5pq5","title":"atomic-agents-stack: Parallel helper/delegate batch reserves $0 for models absent from the pricing table, bypassing the cost-cap fan-out guard","description":"`_estimate_batch_cost` (`atomic_agents/agent.py`) looks up the per-model output price with `PRICING.get(model, {})`, returning 0.0 for any model not in the hardcoded pricing table. `_check_batch_reservation` then early-returns when the reservation is \u003c= 0, skipping the batch reservation entirely. That reservation is the only defense against the documented fan-out race where every parallel helper/delegate reads the identical pre-batch on-disk cost total and each passes its individual check even though the collective spend overruns the configured cap.\n\n**Impact:** an operator running any model not in the pricing table (self-hosted/Ollama/vLLM, a new provider SKU) with `cost_guardrails` + `daily_cap_usd` set believes the cap protects them, but a single parallel batch can blow past the cap. The parallel-helper `model` argument can also be steered to an unknown id. The sibling `dream._estimate_dream_cost` does this correctly (`PRICING.get(model, _fallback_pricing())`), which makes this a clear defect.\n\n**Affected:** `agent.py` (`_estimate_batch_cost` / `_check_batch_reservation`), all versions through 1.0.0.\n\n**Fix:** use `PRICING.get(model, _costs._fallback_pricing())['output']` (mirror dream/calc_cost). Add a conformance test asserting an unknown-model batch reserves \u003e 0 and that an over-cap unknown-model batch raises `CostGuardrailBlocked`.","status":"published","published":"2026-08-17T21:50:01Z","modified":"2026-09-16T03:56:06.072717965Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T15:46:49.977351Z"}]}}