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Medium, CVSS 5.9amended

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

CVE-2026-63405GHSA-5p54-whvp-x327

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Go github.com/anycable/anycable

    Affected
    <= 1.6.14
    Fixed in
    1.6.15

  • Go github.com/anycable/anycable-go

    Affected
    every version
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS
  • CVE-2026-63405: 0.21% estimated exploitation activity in the next 30 days; percentile 11.03 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary The Pusher-compatible REST API includes bodymd5 in the HMAC signature string but never computes or verifies the MD5 of the received HTTP body, allowing anyone who observes a signed request to replay it with an entirely different body. Details In pusher/http.go, the Handler function extracts bodymd5 from the URL query string (line 169) and includes it verbatim in stringToSign (line 175). It then verifies HMAC(stringToSign, secret) == authsignature. After verification succeeds, handleEvents reads and parses r.Body (lines 201-212) without ever computing md5(body) and comparing it against the bodymd5 that was signed. The Pusher protocol specification explicitly requires the server to verify this digest to prevent body-substitution attacks. There is also no authtimestamp staleness check, so replays are valid indefinitely. PoC 1. Capture a legitimate signed POST to /apps/<appid/events?authkey=K&authtimestamp=T&authversion=1.0&bodymd5=LEGITMD5&authsignature=SIG carrying body…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-5p54-whvp-x327

  2. Revision 2 · amended ·

    Amended from osv record GO-2026-6516

  3. Revision 1 · created ·

    Published from osv record GHSA-5p54-whvp-x327

Agent brief

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# Patch Next advisory brief: CVE-2026-63405

Advisory: AnyCable: Pusher REST API Does Not Verify Request Body MD5 Enabling Signed-Request Replay with Arbitrary Body
IDs: CVE-2026-63405, GHSA-5p54-whvp-x327
Record: https://patchnext.com/advisories/cve-2026-63405 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/anycable/anycable 1.6.15. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/anycable/anycable: affected <= 1.6.14; fixed in 1.6.15
- Go github.com/anycable/anycable-go: affected every version

## Suggested inspection (read-only)
- Go github.com/anycable/anycable: check the installed version with your package manager.
- Go github.com/anycable/anycable-go: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/anycable/anycable, github.com/anycable/anycable-go.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-5p54-whvp-x327 (OSV record GHSA-5p54-whvp-x327 lists affected ranges: Go github.com/anycable/anycable >=0 <1.6.15 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6516 (OSV record GO-2026-6516 lists affected ranges: Go github.com/anycable/anycable-go >=0)
- Verified: https://github.com/advisories/GHSA-5p54-whvp-x327 (GitHub-reviewed advisory GHSA-5p54-whvp-x327 lists affected ranges: Go github.com/anycable/anycable >=0 <=1.6.14)

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