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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_token

Quick assessment

Affected
CVE-2026-72887
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Net::OAuth::Client 在 0.32 版本之前的 Perl 实现中，允许服务提供者在 get_request_token 阶段 silently（静默）将 OAuth 1.0a 降级为 OAuth 1.0。 当向构造函数传递一个回调参数时，该模块会选择使用 OAuth 1.0a。然而，在获取令牌（request token）的响应中，如果未返回 oauth_callback_confirmed 字段，Net::OAuth::Client 会撤销此前选择的 OAuth 1.0a 协议，且在此过程中既不抛

AI Predicted 8.1 Difficulty: Moderate EPSS 0.55% · P44

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
None None < 0.32 affected

I. Basic Information for CVE-2026-72887

Vulnerability Information
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Vulnerability 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
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
在会话协商时选择低安全性的算法(算法降级)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
- - 0 ~ 0.32 -

II. Public POCs for CVE-2026-72887

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III. Intelligence Information for CVE-2026-72887

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Patches & Fixes for CVE-2026-72887 (2)

Vendor Advisories for CVE-2026-72887 (1)

IV. Related Vulnerabilities

Same weakness: CWE-757

V. Comments for CVE-2026-72887

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