CVE-2026-3783
Received Received - Intake
OAuth2 Token Leakage via Redirects in curl HTTP Transfers

Publication date: 2026-03-11

Last updated on: 2026-03-12

Assigner: curl

Description
When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer performs a redirect to a second URL, curl could leak that token to the second hostname under some circumstances. If the hostname that the first request is redirected to has information in the used .netrc file, with either of the `machine` or `default` keywords, curl would pass on the bearer token set for the first host also to the second one.
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Meta Information
Published
2026-03-11
Last Modified
2026-03-12
Generated
2026-06-16
AI Q&A
2026-03-11
EPSS Evaluated
2026-06-14
NVD
CVE-2026-3783
EUVD
EUVD-2026-11138
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
haxx curl From 7.33.0 (inc) to 8.19.0 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-522 The product transmits or stores authentication credentials, but it uses an insecure method that is susceptible to unauthorized interception and/or retrieval.
Attack-Flow Graph
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Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-3783 is a medium-severity vulnerability in curl versions 7.33.0 through 8.18.0 involving the leakage of OAuth2 bearer tokens during HTTP(S) redirects.'}, {'type': 'paragraph', 'content': "When a curl transfer uses an OAuth2 bearer token and encounters a redirect to a second URL, curl may inadvertently send the bearer token to the redirected hostname if that hostname is present in the user's .netrc file under the machine or default keywords."}, {'type': 'paragraph', 'content': 'This results in the token being exposed to an unintended host due to insufficiently protected credentials (CWE-522).'}] [1, 2, 3]

Impact Analysis

This vulnerability can lead to the unintended exposure of OAuth2 bearer tokens to unauthorized hosts during HTTP(S) redirects.

If an attacker controls or has access to the redirected hostname listed in the .netrc file, they could receive the bearer token and potentially use it to gain unauthorized access to protected resources or services.

This compromises the confidentiality and security of authentication credentials, increasing the risk of unauthorized access and data breaches.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

To mitigate this vulnerability, users are advised to upgrade curl to version 8.19.0 or later, where the issue has been fixed.

Alternatively, users can apply the patch and rebuild libcurl if they are using it in their applications.

As an additional mitigation, avoid using OAuth2 bearer tokens with HTTP(S) redirects to prevent the token from being leaked to unintended hosts.

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