{"id":"GHSA-mph8-9v29-pm42","aliases":[],"status":"published","title":"axonflow-sdk-typescript: Webhook signing-key (HMAC-SHA256) not exposed by SDK type, preventing signature verification","description":"## Summary\n\nThe AxonFlow SDK's `WebhookSubscription` (or equivalent) type did not expose the HMAC-SHA256 signing key returned by the platform's `CreateWebhook` endpoint. Without access to the secret through the typed SDK API, callers had no path to verify the `X-AxonFlow-Signature` header on incoming webhook deliveries. Affected callers had two unsatisfactory options:\n\n1. Skip signature verification entirely — accepting any payload from any source that knew the webhook URL.\n2. Hand-parse the raw HTTP JSON response to extract the secret, bypassing the type-safe SDK surface.\n\nThis advisory is filed across all four AxonFlow SDKs (Go, Python, TypeScript, Java) because the same defect and the same fix landed in each.\n\n## Affected versions\n\nVersions 5.6.0 and below.\n\n## Impact\n\nA webhook receiver using the SDK's typed API to handle inbound deliveries had no path to authenticate the source of incoming payloads. An attacker who learned the webhook URL — through misconfiguration, log leakage, observable network traffic during setup, or any other discovery channel — could forge webhook deliveries indistinguishable from legitimate ones, causing the receiving application to act on fabricated events (e.g. simulated approval-granted callbacks, simulated policy-decision callbacks, simulated step-completion callbacks).\n\n## Remediation\n\nUpgrade to the patched version listed in Vulnerabilities below. The signing key is now exposed on the `WebhookSubscription` response type returned by `CreateWebhook`. Implementations should:\n\n1. Persist the secret returned by `CreateWebhook` securely (it is only returned once, at create time).\n2. On each incoming webhook delivery, compute `HMAC-SHA256(secret, raw_body)` and compare it in constant time against the `X-AxonFlow-Signature` header.\n3. Reject any delivery whose signature does not match.\n\n## Credit\n\nIdentified by AxonFlow internal security review during the April 2026 quality-freeze epic.","severity":{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium","from":"ghsa"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-345","CWE-347"],"published":"2026-05-06T23:16:24Z","modified":"2026-05-06T23:35:57Z","fixes":[{"ecosystem":"npm","package":"@axonflow/sdk","fixed_in":["6.0.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"@axonflow/sdk","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.0.0"}]}]},{"source":"osv","ecosystem":"npm","package":"@axonflow/sdk","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"6.0.0"}]}]}],"references":[{"url":"https://github.com/getaxonflow/axonflow-sdk-typescript/security/advisories/GHSA-mph8-9v29-pm42","tags":["web"]},{"url":"https://github.com/advisories/GHSA-mph8-9v29-pm42"},{"url":"https://github.com/getaxonflow/axonflow-sdk-typescript","tags":["package"]}],"sources":{"ghsa":[{"id":"GHSA-mph8-9v29-pm42","title":"axonflow-sdk-typescript: Webhook signing-key (HMAC-SHA256) not exposed by SDK type, preventing signature verification","description":"## Summary\n\nThe AxonFlow SDK's `WebhookSubscription` (or equivalent) type did not expose the HMAC-SHA256 signing key returned by the platform's `CreateWebhook` endpoint. Without access to the secret through the typed SDK API, callers had no path to verify the `X-AxonFlow-Signature` header on incoming webhook deliveries. Affected callers had two unsatisfactory options:\n\n1. Skip signature verification entirely — accepting any payload from any source that knew the webhook URL.\n2. Hand-parse the raw HTTP JSON response to extract the secret, bypassing the type-safe SDK surface.\n\nThis advisory is filed across all four AxonFlow SDKs (Go, Python, TypeScript, Java) because the same defect and the same fix landed in each.\n\n## Affected versions\n\nVersions 5.6.0 and below.\n\n## Impact\n\nA webhook receiver using the SDK's typed API to handle inbound deliveries had no path to authenticate the source of incoming payloads. An attacker who learned the webhook URL — through misconfiguration, log leakage, observable network traffic during setup, or any other discovery channel — could forge webhook deliveries indistinguishable from legitimate ones, causing the receiving application to act on fabricated events (e.g. simulated approval-granted callbacks, simulated policy-decision callbacks, simulated step-completion callbacks).\n\n## Remediation\n\nUpgrade to the patched version listed in Vulnerabilities below. The signing key is now exposed on the `WebhookSubscription` response type returned by `CreateWebhook`. Implementations should:\n\n1. Persist the secret returned by `CreateWebhook` securely (it is only returned once, at create time).\n2. On each incoming webhook delivery, compute `HMAC-SHA256(secret, raw_body)` and compare it in constant time against the `X-AxonFlow-Signature` header.\n3. Reject any delivery whose signature does not match.\n\n## Credit\n\nIdentified by AxonFlow internal security review during the April 2026 quality-freeze epic.","status":"published","published":"2026-05-06T23:16:24Z","modified":"2026-05-06T23:16:25Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-345","CWE-347"],"updated_at":"2026-11-02T14:40:02.883746Z"}],"osv":[{"id":"GHSA-mph8-9v29-pm42","title":"axonflow-sdk-typescript: Webhook signing-key (HMAC-SHA256) not exposed by SDK type, preventing signature verification","description":"## Summary\n\nThe AxonFlow SDK's `WebhookSubscription` (or equivalent) type did not expose the HMAC-SHA256 signing key returned by the platform's `CreateWebhook` endpoint. Without access to the secret through the typed SDK API, callers had no path to verify the `X-AxonFlow-Signature` header on incoming webhook deliveries. Affected callers had two unsatisfactory options:\n\n1. Skip signature verification entirely — accepting any payload from any source that knew the webhook URL.\n2. Hand-parse the raw HTTP JSON response to extract the secret, bypassing the type-safe SDK surface.\n\nThis advisory is filed across all four AxonFlow SDKs (Go, Python, TypeScript, Java) because the same defect and the same fix landed in each.\n\n## Affected versions\n\nVersions 5.6.0 and below.\n\n## Impact\n\nA webhook receiver using the SDK's typed API to handle inbound deliveries had no path to authenticate the source of incoming payloads. An attacker who learned the webhook URL — through misconfiguration, log leakage, observable network traffic during setup, or any other discovery channel — could forge webhook deliveries indistinguishable from legitimate ones, causing the receiving application to act on fabricated events (e.g. simulated approval-granted callbacks, simulated policy-decision callbacks, simulated step-completion callbacks).\n\n## Remediation\n\nUpgrade to the patched version listed in Vulnerabilities below. The signing key is now exposed on the `WebhookSubscription` response type returned by `CreateWebhook`. Implementations should:\n\n1. Persist the secret returned by `CreateWebhook` securely (it is only returned once, at create time).\n2. On each incoming webhook delivery, compute `HMAC-SHA256(secret, raw_body)` and compare it in constant time against the `X-AxonFlow-Signature` header.\n3. Reject any delivery whose signature does not match.\n\n## Credit\n\nIdentified by AxonFlow internal security review during the April 2026 quality-freeze epic.","status":"published","published":"2026-05-06T23:16:24Z","modified":"2026-05-06T23:35:57.327389Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-345","CWE-347"],"updated_at":"2026-11-02T15:46:52.170928Z"}]}}