SEPTEMBER 17, 2026
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Case File

CVE-2026-72887

CRITICAL · CVSS 9.8 EPSS 0.55% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-08-16 · Last synced 2026-09-15

CyberRota Analysis

AI-Generated

Net::OAuth::Client versions prior to 0.32 for Perl are vulnerable to a silent downgrade from OAuth 1.0a to OAuth 1.0 during the get_request_token process, which can lead to session fixation attacks. This flaw allows an attacker to exploit the lack of an oauth_verifier in the access token request, potentially linking a victim's account to an attacker's session without any warning or exception. Organizations using affected versions of Exchange should prioritize patching this vulnerability to safeguard against unauthorized access and account compromise.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-72887
Severity
CRITICAL
CVSS
9.8
EPSS
0.55%
Exchange

Original NVD 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.