CVE WatchAug 16, 2026

CVE-2026-72887

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_tok

CVSS

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No CVSS

EPSS

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KEV

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Exploit Today

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0-100

Published: Aug 16, 2026 · Last modified: Aug 16, 2026 · CWE-757

EPSS · 30d

Not enough EPSS history yet.

Technical 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.

Official references

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