{"cve":"CVE-2026-1664","nvd":{"published":"2026-02-03T12:16:11.953","modified":"2026-06-17T10:16:16.637","status":"Deferred","description":"Summary\n\nAn Insecure Direct Object Reference has been found to exist in `createHeaderBasedEmailResolver()` function within the Cloudflare Agents SDK. The issue occurs because the `Message-ID` and `References` headers are parsed to derive the target agentName and agentId without proper validation or origin checks, allowing an external attacker with control of these headers to route inbound mail to arbitrary Durable Object instances and namespaces .\n\n\n\n\nRoot cause\n\nThe `createHeaderBasedEmailResolver()` function lacks cryptographic verification or origin validation for the headers used in the routing logic, effectively allowing external input to dictate internal object routing.\n\n\n\n\nImpact\n\nInsecure Direct Object Reference (IDOR) in email routing lets an attacker steer inbound mail to arbitrary Agent instances via spoofed Message-ID.\n\n\n\n\n\nMitigation:\n\n  *  PR:  https://github.com/cloudflare/agents/blob/main/docs/email.md ] provides the necessary architectural context for coding agents to mitigate the issue by refactoring the resolver to enforce strict identity boundaries.\n  *  Agents-sdk users should  upgrade to agents@0.3.7","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N","score":6.9},"cvss_v3":null,"cwes":["CWE-639"],"references":["https://github.com/cloudflare/agents"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:22:27.261130201+00:00"},"epss":{"cve":"CVE-2026-1664","score":0.00465,"percentile":0.40272,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-r7x9-8ph7-w8cg","url":"https://osv.dev/vulnerability/GHSA-r7x9-8ph7-w8cg","summary":"Cloudflare Agents SDK has Insecure Direct Object Reference (IDOR) via Header-Based Email Routing","modified":"2026-02-22T23:26:19.292614Z","packages":[{"ecosystem":"npm","name":"agents","purl":"pkg:npm/agents","ranges":["<0.3.7"],"fixed":["0.3.7"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}