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.
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| unaffected |
|
No data.
No data.
No data available yet.
Vendor Solution
Upgrade to Net-OAuth 0.32 or later.
Tracking
Sign in to view the affected projects.
No advisories yet.
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
No data.
MITRE
Status: PUBLISHED
Assigner: CPANSec
Published:
Updated: 2026-08-16T17:06:04.526Z
Reserved: 2026-08-10T15:44:58.172Z
Link: CVE-2026-72887
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-16T14:16:54.860
Modified: 2026-08-16T17:17:41.493
Link: CVE-2026-72887
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-08-16T15:30:04Z
-
CWE-757
Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')