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CVE-2026-54603 is a high-severity vulnerability in the ruby-oauth2 gem affecting versions 0.4.0 through 2.0.21. The flaw is in redirect handling within OAuth2::Client#request, where a protocol-relative HTTP Location value beginning with "//" is resolved in a way that replaces the original request authority while preserving request options and sensitive headers. When the client follows such a redirect, the bearer Authorization header from the original request can be forwarded to an attacker-controlled host. In addition to credential leakage, the same behavior can be abused to induce server-side requests to attacker-selected destinations, creating an SSRF condition. The issue affects backend OAuth 2.0 and OIDC flows that automatically follow redirects and was fixed in version 2.0.22 by safely resolving redirect targets and removing Authorization headers on cross-origin redirects.
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An information disclosure and open redirect-related vulnerability in the ruby-oauth oauth2 gem where a protocol-relative redirect can cause the bearer Authorization header to be sent to an attacker-controlled host, leaking credentials.
A high-severity vulnerability in the ruby-oauth2 gem where protocol-relative redirects can cause bearer tokens to be forwarded to attacker-controlled hosts and enable SSRF.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.