CVE-2026-54603
OAuth2 Ruby gem leaks bearer tokens via protocol-relative redirect override.
Is CVE-2026-54603 being exploited?
Not confirmed. CVE-2026-54603 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.43% probability of exploitation in the next 30 days.
How severe is CVE-2026-54603?
CVE-2026-54603 is rated High with a CVSS score of 8.6. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-54603?
Yes. A fix has been recorded for CVE-2026-54603. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-54603 affect?
CVE-2026-54603 affects oauth2 Ruby gem 0.4.0 - 2.0.21, Ruby web applications using the oauth2 gem. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-54603?
Upgrade oauth2 gem to 2.0.22 immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Protocol-relative redirect can override request authority causing Authorization bearer token to be sent to attacker-controlled host, enabling token theft and account/session takeover.
Patch when possible
- affected>= 0.4.0 and < 2.0.22
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.