CVE-2026-63403: Faktory: Unrecovered panic in command handlers allows full-server denial of service

Published Aug 25, 2026
·
Updated

Faktory is a language-agnostic background job server. In versions prior to 1.10.0, the server is vulnerable to an unauthenticated denial of service in which a single malformed command crashes the entire process. Its wire protocol is line-based, and several command handlers slice or index the received line at a fixed offset, such as cmd[5:] for PUSH or qs[0] for QUEUE, without checking that a payload is present. Sending a bare verb with no payload, for example PUSH, ACK, FAIL, BEAT, PUSHB, or QUEUE, triggers a Go slice or index out-of-range panic. Because the codebase has no recover() anywhere in the command-dispatch path, an unrecovered panic in a handler goroutine terminates the whole Go process rather than just that connection, instantly disconnecting every other client, worker, and in-flight job. The attack requires only a connection to the command port and completion of the trivial handshake, with no credentials when no password is configured, and can be repeated to keep the service down indefinitely. This issue is fixed in version 1.10.0.

Affected Software

1 affected component
Faktory<1.10.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade Faktory to a version that resolves this vulnerability.

    Fixed in 1.10.0

Event History

Aug 25, 2026
CVE Published
via MITRE·10:04 PM
Data Sourced
via MITRE·10:04 PM
DescriptionWeakness
Data Sourced
via NVD·10:17 PM
DescriptionSeverityWeakness

Frequently Asked Questions

1

Which deployments are exposed to unauthenticated attacks?

Any affected Faktory server whose command port is reachable by an attacker and has no password configured can be crashed without credentials. The attacker only needs to complete the protocol handshake and send a malformed bare command.

2

What is required to exploit the issue?

Exploitation requires network access to the Faktory command port and a trivial handshake. A bare command such as PUSH, ACK, FAIL, BEAT, PUSHB, or QUEUE can trigger the unrecovered panic when no required payload is supplied.

3

What is the operational impact of a successful attack?

The panic terminates the entire Faktory process, disconnecting all clients and workers and interrupting in-flight jobs. The attack can be repeated to keep the service unavailable.

4

Which versions need remediation?

Faktory versions prior to 1.10.0 are affected. Upgrade to version 1.10.0 to obtain the fix.

Contact

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