CVE-2026-63687
Apache CXF flaw lets signed JWT override PKCE/OIDC params, enabling auth bypass
Is CVE-2026-63687 being exploited?
Not confirmed. CVE-2026-63687 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 0.27% probability of exploitation in the next 30 days.
How severe is CVE-2026-63687?
CVE-2026-63687 is rated Critical with a CVSS score of 9.1. 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-2026-63687?
Yes. A fix has been recorded for CVE-2026-63687. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-63687 affect?
CVE-2026-63687 affects Apache CXF JwtRequestCodeFilter (versions prior to 4.2.3, 4.1.8, 3.6.12), Applications using Apache CXF for OAuth/OpenID Connect flows. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-63687?
Upgrade to CXF 4.2.3/4.1.8/3.6.12 and rotate client secrets immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker with a valid signed request JWT (e.g., stolen client_secret) can overwrite code_challenge, nonce, state to bypass PKCE/OIDC, enabling auth-code replay or session takeover.
Immediate action required
- affected>= 4.2.0 and < 4.2.3
- affected>= 4.0.0 and < 4.1.8
- affected< 3.6.12
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.