Description
Net::OAuth::Client versions before 0.32 for Perl allow the service provider to silently downgrade OAuth 1.0a to OAuth 1.0 in get_request_token.

Passing a callback to the constructor selects OAuth 1.0a. get_request_token then revokes that choice when the request token response omits oauth_callback_confirmed, with no exception, no warning and no option to require 1.0a. The access token request is built from the OAuth 1.0 message class, which has no verifier parameter, so oauth_verifier is dropped from the request even when get_access_token was passed one.

oauth_verifier is the binding that OAuth 1.0a added between the authorization step and the token exchange. An application that asked for 1.0a and gets 1.0 is open to OAuth 1.0 session fixation, where an attacker obtains a request token, has the victim authorize it, and then completes the exchange themselves, linking the victim's provider account to a session the attacker controls. No attacker action sets up the downgrade: a provider that does not confirm the callback is enough.
Published: 2026-08-16
Score: 9.8 Critical
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

Vendor Solution

Upgrade to Net-OAuth 0.32 or later.

Tracking

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History

Mon, 17 Aug 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Mon, 17 Aug 2026 11:30:00 +0000

Type Values Removed Values Added
First Time appeared Vurtdev
Vurtdev net-oauth
Vendors & Products Vurtdev
Vurtdev net-oauth

Sun, 16 Aug 2026 17:30:00 +0000

Type Values Removed Values Added
References

Sun, 16 Aug 2026 14:00:00 +0000

Type Values Removed Values Added
Description Net::OAuth::Client versions before 0.32 for Perl allow the service provider to silently downgrade OAuth 1.0a to OAuth 1.0 in get_request_token. Passing a callback to the constructor selects OAuth 1.0a. get_request_token then revokes that choice when the request token response omits oauth_callback_confirmed, with no exception, no warning and no option to require 1.0a. The access token request is built from the OAuth 1.0 message class, which has no verifier parameter, so oauth_verifier is dropped from the request even when get_access_token was passed one. oauth_verifier is the binding that OAuth 1.0a added between the authorization step and the token exchange. An application that asked for 1.0a and gets 1.0 is open to OAuth 1.0 session fixation, where an attacker obtains a request token, has the victim authorize it, and then completes the exchange themselves, linking the victim's provider account to a session the attacker controls. No attacker action sets up the downgrade: a provider that does not confirm the callback is enough.
Title Net::OAuth::Client versions before 0.32 for Perl allow the service provider to silently downgrade OAuth 1.0a to OAuth 1.0 in get_request_token
Weaknesses CWE-757
References

Subscriptions

Vurtdev Net-oauth
cve-icon MITRE

Status: PUBLISHED

Assigner: CPANSec

Published:

Updated: 2026-08-17T16:29:31.019Z

Reserved: 2026-08-10T15:44:58.172Z

Link: CVE-2026-72887

cve-icon Vulnrichment

Updated: 2026-08-16T17:06:04.526Z

cve-icon NVD

Status : Received

Published: 2026-08-16T14:16:54.860

Modified: 2026-08-17T17:16:50.360

Link: CVE-2026-72887

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-17T19:00:05Z

Weaknesses