PrefectHQ prefect Webhook/Notification validate_restricted_url toctou
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.
- Published
- May 3, 2026
- Updated
- Jun 17, 2026
- EPSS
- 0.3% · 22th percentile
- CWE
- CWE-362
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Report tools
Action score
5
Monitor
Low priority for now.
- CVSS
- 5 / 40 · 1.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- proof of concept
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · VulDB
- 2.3
- NVD has not scored this yet; the score shown is the CNA’s.
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
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (VulDB). Independent of NVD's CPE analysis and usually ahead of it.
PrefectHQ prefect
- 3.6.28.dev2not affected
- 3.6.28.dev1affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| PyPI | prefect | before 3.6.28.dev2 | 3.6.28.dev2 |
Same product
prefecthq: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-72538PrefectHQ Prefect - Argument Injection35Monitor
- CVE-2026-7723PrefectHQ prefect WebSocket Endpoint in missing authentication22Monitor
- CVE-2026-7722PrefectHQ prefect Health Check API health endswith improper authentication22Monitor
- CVE-2026-7725PrefectHQ prefect GitRepository Pull storage.py argument injection8Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| PrefectHQ prefect | 3.6.28.dev2 · description | Vendor (CNA) |
| PyPI:prefect | 3.6.28.dev2 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- VulDB CNA Teamcoordinator
- nedlir (VulDB User)reporter
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
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Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- A low-privileged account is enough.
- No user action is required.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- Integrity
- Availability
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- X
Weakness class (CWE)
CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')CVSS 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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
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Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- gist.github.com/nedlir/fa99777e8989414585d08c3625bf044a
- github.com/PrefectHQ/prefect/
- github.com/PrefectHQ/prefect/commit/7c70ac54a5e101431d83b9f2681ec88d5e0021ed
- github.com/PrefectHQ/prefect/pull/21591
- github.com/PrefectHQ/prefect/releases/tag/3.6.28.dev2
- linear.app/prefect/issue/OSS-7874/fix-dns-rebinding-toctou-bypass-in-validate-restricted-url
- vuldb.com/submit/807303
- vuldb.com/vuln/360900
- vuldb.com/vuln/360900/cti
Vendor advisories and official records. Exploit/PoC links are deliberately left out.