GHSA-MHC4-QQ83-FMRR

The 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:

1. Skip signature verification entirely, accepting any payload from any source that knew the webhook URL.
2. Hand-parse the raw HTTP JSON response to extract the secret, bypassing the type-safe SDK surface.

This advisory is filed across all four AxonFlow SDKs (Go, Python, TypeScript, Java) because the same defect and the same fix landed in each.

Affected versions

Versions 5.6.1 and below.

Credit

Identified by AxonFlow internal security review during the April 2026 quality-freeze epic.

A 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).

GHSA-MHC4-QQ83-FMRR has a CVSS score of 5.9 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.7.0); upgrading removes the vulnerable code path.

Kodem intelligence

Upgrade to the patched version listed in Vulnerabilities below. The signing key is now exposed on the WebhookSubscription response type returned by CreateWebhook. Implementations should:

1. Persist the secret returned by CreateWebhook securely (it is only returned once, at create time).
2. On each incoming webhook delivery, compute HMAC-SHA256(secret, raw_body) and compare it in constant time against the X-AxonFlow-Signature header.
3. Reject any delivery whose signature does not match.

1. What is GHSA-MHC4-QQ83-FMRR? GHSA-MHC4-QQ83-FMRR is a medium-severity security vulnerability in github.com/getaxonflow/axonflow-sdk-go/v5 (go), affecting versions < 5.7.0. It is fixed in 5.7.0.
2. How severe is GHSA-MHC4-QQ83-FMRR? GHSA-MHC4-QQ83-FMRR has a CVSS score of 5.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/getaxonflow/axonflow-sdk-go/v5 are affected by GHSA-MHC4-QQ83-FMRR? github.com/getaxonflow/axonflow-sdk-go/v5 (go) versions < 5.7.0 is affected.
4. Is there a fix for GHSA-MHC4-QQ83-FMRR? Yes. GHSA-MHC4-QQ83-FMRR is fixed in 5.7.0. Upgrade to this version or later.
5. Is GHSA-MHC4-QQ83-FMRR exploitable, and should I be worried? Whether GHSA-MHC4-QQ83-FMRR is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-MHC4-QQ83-FMRR is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-MHC4-QQ83-FMRR? Upgrade github.com/getaxonflow/axonflow-sdk-go/v5 to 5.7.0 or later.