NVD / CVE Program· CNA GitHub_M

CVE-2026-33511: pyload-ng: Authentication Bypass via Host Header Injection in ClickNLoad

HighCVSS 8.8 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 35/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.44% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: pyload pyload 0.5.0b3.dev97.

Low priority for now. Upgrade to pyload pyload 0.5.0b3.dev97 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

pyLoad is a free and open-source download manager written in Python. From version 0.4.20 to before version 0.5.0b3.dev97, the local_check decorator in pyLoad's ClickNLoad feature can be bypassed by any remote attacker through HTTP Host header spoofing. This allows unauthenticated remote users to access localhost-restricted endpoints, enabling them to inject arbitrary downloads, write files to the storage directory, and execute JavaScript code. This issue has been patched in version 0.5.0b3.dev97.

Published: Mar 24, 2026
Updated: Jun 17, 2026
EPSS: 0.4% · 39th percentile
CWE: CWE-639

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 35 / 40 · 8.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CISA SSVC decision

Exploitation: proof of concept
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · GitHub_M: 8.8; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:L/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
pyload	pyload	cpe:2.3:a:pyload:pyload
pyload-ng project	pyload-ng	cpe:2.3:a:pyload-ng_project:pyload-ng

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

pyload pyload
- >= 0.4.20, < 0.5.0b3.dev97affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

pyload pyloadup to 0.4.20 inclusive
pyload-ng project pyload-ng0.5.0a5.dev528 and later · before 0.5.0b3.dev97

Same product

pyload: all records

Other highest-scoring records for the same primary product.

CVE-2023-0297Code Injection in pyload/pyload
68This week
CVE-2024-21644pyLoad unauthenticated flask configuration leakage
43Plan
CVE-2025-53890pyLoad vulnerable to remote code execution through js2py onCaptchaResult
39Monitor

Published before and after this one in the same product

← EarlierCVE-2026-32808Mar 19, 2026 · pyLoad: Arbitrary File Deletion via Path Traversal during Encrypted 7z Password Verification
32Monitor
← EarlierCVE-2026-33509Mar 24, 2026 · pyload-ng: SETTINGS Permission Users Can Achieve Remote Code Execution via Unrestricted Reconnect Script Configuration
35Monitor
Later →CVE-2026-33992Mar 27, 2026 · pyLoad: Server-Side Request Forgery via Download Link Submission Enables Cloud Metadata Exfiltration
37Monitor

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
pyload pyload	0.5.0b3.dev97 · description	Vendor (CNA)

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.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

CVE-2026-339923 days apartpyLoad: Server-Side Request Forgery via Download Link Submission Enables Cloud Metadata Exfiltration
37Monitor
CVE-2026-335090 days apartpyload-ng: SETTINGS Permission Users Can Achieve Remote Code Execution via Unrestricted Reconnect Script Configuration
35Monitor
CVE-2026-3546414 days apartpyLoad has an incomplete fix for CVE-2026-33509: unprotected storage_folder enables arbitrary file write to Flask session store and code execution
30Monitor
CVE-2026-4656165 days apartpyLoad: SSRF via HTTP Redirect Bypass in parse_urls API
20Monitor

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · public bounty program.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: X

Weakness class (CWE)

CWE-639 · Authorization Bypass Through User-Controlled Key

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:L/SA:N/E:X/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

Root cause

The endpoint fetches the record by the ID sent in the request, but never checks whether the record belongs to the requesting user.

The bug in code

The whole CWE-639 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1const invoice = await Invoice.findById(req.params.id);
2res.json(invoice);

Fixed

1const invoice = await Invoice.findOne({
2  id: req.params.id,
3  ownerId: req.user.id,
4});
5if (!invoice) return res.sendStatus(404);
6res.json(invoice);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log (1)

Fix✗ → ✓Sep 29, 2026, 11:55 AM UTC

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