Not ratedCVE-2026-49272

Oauthlib: Improper Authentication (CVE-2026-49272)

Published 27.10.2026Sources: OSV, Hersteller

What is affected, what to do

Update Oauthlib to version 4.0.0.

Affected: Oauthlib 3.3.0..*
Oauthlib 3.3.1..*
Oauthlib *..>= 3.3.0, < 4.0.0
Fixed in: Oauthlib 4.0.0

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Metrics

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Priority

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CVSS v3

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EPSS score

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Severity: Not rated
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 30.00 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: no public PoC known
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 27.10.2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-287

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

Summary

A call to the token endpoint with a grant type of "urn:ietf:params:oauth:grant-type:device_code" and a bogus device_code is able to get a bearer token as long as they know a valid client ID enabled for the device workflow.

Details

Section 3.4 of the RFC 8628 spec says that the token endpoint should take in device_code as a required parameter.DeviceCodeGrant.validate_token_request does not perform any validation of device_code. DeviceCodeGrant.validate_token_request should be validating that device_code was passed in as a parameter and that it is valid, similar to how AuthorizationCodeGrant.validate_token_request does the checks here and here.

I would like to propose a new method be added to RequestValidator called validate_device_code that is similar to the validate_code method and is called inside of DeviceCodeGrant.validate_token_request.

PoC

Create an implementation of RequestValidation.authenticate_client that returns True if the client's client_type is "public". You would find yourself in this scenario because there's another issue with DeviceCodeGrant.validate_token_request where it doesn't properly handle public clients (see https://github.com/oauthlib/oauthlib/issues/919).

Create a client that has a client_type of "public" and set it's grant_type to "urn:ietf:params:oauth:grant-type:device_code".

With this implementation of RequestValidation.authenticate_client done, use that validator for your token endpoint. Call the token endpoint with a body of

{
  "client_id": <ID of the public client you made>,
  "grant_type": "urn:ietf:params:oauth:grant-type:device_code",
  "device_code": <anything you want since it's not validated>
}

You now have a bearer token for the client without a valid device_code.

Impact

Anyone using the RFC 8628 device workflow in oauthlib that doesn't realize the device_code parameter is not being validated.

Source: OSV (Open Source Vulnerabilities), GitHub Security Advisories

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
pip	oauthlib	`>= 3.3.0, < 4.0.0`	`4.0.0`
pypi	oauthlib	`3.3.0` `3.3.1`	`4.0.0` —

Weakness classes (CWE)

CWE-287Improper Authentication
Class
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
Entry at MITRE CWE-287

References & sources

github.comoauthlib/oauthlib/security/advisories/GHSA-3jp2-3mrg-2vxcweb
github.comoauthlib/oauthlibpackage
github.comoauthlib/oauthlib/releases/tag/v4.0.0web

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