CVE-2026-72887Network attack vector

Session fixation via silent OAuth protocol downgrade

Published Aug 16, 2026 · Updated Aug 16, 2026

OAuth protocol downgrade in Net-OAuth before 0.32 allows remote attackers to link victim accounts to attacker-controlled sessions. Net::OAuth::Client::get_request_token clears OAuth 1.0a mode when oauth_callback_confirmed is absent, causing the access-token request class to discard oauth_verifier. An OAuth provider must omit callback confirmation, after which an attacker can have a victim authorize a request token and complete the exchange in the attacker's session.

CVSS severity9.8
Critical
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OAuth protocol downgrade in Net-OAuth before 0.32 allows remote attackers to link victim accounts to attacker-controlled sessions. Net::OAuth::Client::get_request_token clears OAuth 1.0a mode when oauth_callback_confirmed is absent, causing the access-token request class to discard oauth_verifier. An OAuth provider must omit callback confirmation, after which an attacker can have a victim authorize a request token and complete the exchange in the attacker's session.

The record

CVE
CVE-2026-72887
Published
Aug 16, 2026
Updated
Aug 16, 2026
Vendor
Robert Rothenberg
Product
Net-OAuth
Classifications
CWE-757, CWE-384, T1550.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <0.32

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Robert Rothenberg · Net-OAuthversion=0 <0.32

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-757Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')
CWE-384Session Fixation
T1550.001Application Access Token

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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