CVE-2026-54603: OAuth2 is a Ruby wrapper for the OAuth 2.0 and 2.1 authorization frameworks, including OpenID Connect (OIDC). From 0.4.0 to 2.0.21, a protocol-relative redirect Location returned t

highCVSS 8.6CVE-2026-54603

OAuth2 is a Ruby wrapper for the OAuth 2.0 and 2.1 authorization frameworks, including OpenID Connect (OIDC). From 0.4.0 to 2.0.21, a protocol-relative redirect Location returned to OAuth2::Client#request overrides the request authority, so the bearer Authorization header is sent to an attacker-controlled host, leaking the credential. This issue is fixed in version 2.0.22.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: high — CVSS 8.6
Published: 2026-07-28
Last updated: 2026-07-29
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-54603

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-546030.27% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 19% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-54603	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

highGHSA-pp92-crg2-gfv9: OAuth2::Client#request: Protocol-relative redirect Location overrides authority, leaking …ghsa

Recent advisories for OAuth2 is a

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highGHSA-xpxj-f2fm-rqch: OliveTin: Unauthenticated DoS via OAuth2 State Memory Exhaustion (Unbounded Map Growth)ghsa · 2026-07-30
highCVE-2026-67437: OliveTin gives access to predefined shell commands from a web interface. From 3000.0.0 until 3…nvd · 2026-07-29
highGHSA-pp92-crg2-gfv9: OAuth2::Client#request: Protocol-relative redirect Location overrides authority, leaking …ghsa · 2026-07-28
mediumGHSA-gh4h-34gr-87r7: Budibase: OAuth2 Token Disclosure via Automation Test Results Broadcast to Other Buildersghsa · 2026-07-24
mediumGHSA-fcrw-f7gg-6g9f: Budibase: SSO OAuth2 Token Leakage via User Metadata Endpoints to Power-Role Usersghsa · 2026-07-24
highGHSA-7488-6r32-c95q: LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallbackghsa · 2026-07-22