CVE-2026-63406: AnyCable: Telemetry Subsystem Contains Hardcoded Authentication Token and Transmits CLI Arguments Including Secrets
Summary The telemetry subsystem embeds a hardcoded auth token ("secret") in the public source and transmits raw CLI arguments—including --secret, --jwtsecret, and --httprpcsecret values—to a third-party telemetry endpoint.
Details In telemetry/config.go line 12, var authToken = "secret" is committed in the public repository and used to authenticate to https://telemetry.anycable.io. In telemetry/telemetry.go, clusterFingerprint() (line 320) calls both anycableFileConfig(c.ConfigFilePath) (line 333), which reads the full TOML config file contents, and anycableCLIArgs() (line 402), which reads os.Args[1:] verbatim—including any --secret=..., --jwtsecret=..., --httprpcsecret=... arguments. Both raw values are passed to generateDigest() (line 373), meaning the actual secret strings flow through the code path and are included in telemetry data sent to the third-party server. Since the hardcoded authToken = "secret" is public, any attacker who can perform DNS hijacking or is positioned on the network path can intercept and read the telemetry payload containing operator credentials.
PoC 1. Read telemetry/config.go in the public repo to find authToken = "secret". 2. Set up a DNS spoof for telemetry.anycable.io pointing to an attacker-controlled server. 3. Start anycable-go with --secret=my-production-secret. 4. The server sends a POST to the attacker's endpoint with the telemetry JSON payload. The clusterFingerprint field contains data derived from raw os.Args including --secret=my-production-secret.
Impact In MITM/DNS-hijack scenarios, production secrets (JWT secrets, broadcast keys, RPC auth) are exposed to third parties. The hardcoded authToken = "secret" provides no protection since it is known to anyone reading the open-source code.
Fix 1. Remove the hardcoded authToken from source; generate or require operator configuration at build time or deployment time. 2. Remove anycableCLIArgs() from the fingerprint computation, or sanitize it to exclude values of secret-bearing flags before hashing. 3. Add a documented opt-out mechanism for telemetry.
Other sources
AnyCable is a realtime server for reliable two-way communication that supports any backend. Prior to 1.6.15, the telemetry subsystem in telemetry/config.go enables tracking with a hardcoded public authToken, while clusterFingerprint in telemetry/telemetry.go reads the full configuration file and raw os.Args returned by anycableCLIArgs, including values supplied through --secret, --jwtsecret, and --httprpcsecret. These inputs are passed to generateDigest, where sha256.New produces the hexadecimal fingerprint that is sent as telemetry. The available source therefore does not show raw credentials leaving the process or establish the advisory's claimed confidentiality loss, although the stable fingerprint is derived from secret-bearing configuration and the default telemetry client uses publicly known authentication material. This issue is fixed in version 1.6.15.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/anycable/anycableto a version that resolves this vulnerability.Fixed in 1.6.15 - Upgrade
Upgrade
anycable-goto a version that resolves this vulnerability.Fixed in 1.6.15 - Configuration
Add/use the documented opt-out mechanism for AnyCable telemetry so operators can disable telemetry collection if desired.
AnyCable telemetry telemetry opt-out mechanism = enabled/available (documented opt-out) - Configuration
Modify telemetry fingerprinting so it does not include raw os.Args values from anycableCLIArgs; remove anycableCLIArgs() from the fingerprint computation or sanitize it to exclude values for secret-bearing flags such as --secret, --jwt_secret, and --http_rpc_secret before hashing.
AnyCable telemetry telemetry data inputs (clusterFingerprint source) = exclude secret-bearing CLI flags - Configuration
Remove the hardcoded telemetry authToken from source (e.g., telemetry/config.go var authToken = "secret") and generate or require it via operator configuration at build time or deployment time.
AnyCable telemetry authToken = do not hardcode (use operator configuration at build/deploy time)
Event History
Frequently Asked Questions
Which deployments are exposed?
AnyCable versions before 1.6.15 are affected when the telemetry subsystem is used. The risk is most relevant to deployments that supply secrets through the configuration file or CLI options such as --secret, --jwt_secret, or --http_rpc_secret.
Does exploitation require an attacker to authenticate or interact with the AnyCable service?
No privileges or user interaction are indicated by the provided vector. However, attack complexity is rated high, and the available source does not show raw credentials being transmitted or establish a direct confidentiality loss.
What data contributes to the telemetry fingerprint?
The cluster fingerprint is derived from the full configuration file and raw command-line arguments. This can include values passed through secret-bearing CLI options, although the transmitted value is a SHA-256 hexadecimal digest rather than the raw argument values.
What is the remediation?
Upgrade AnyCable to version 1.6.15, which fixes the issue. If an immediate upgrade is not possible, avoid placing secrets in the affected CLI arguments or configuration inputs used to generate telemetry fingerprints.
How can I determine whether my deployment needs attention?
Check whether the AnyCable version is earlier than 1.6.15 and whether telemetry is enabled. Also review startup arguments and configuration for --secret, --jwt_secret, --http_rpc_secret, or other secret-bearing values that could be included in the fingerprint.