CVE-2026-55638
Auth bypass in 9Router /codex rewrite allows unauthorized LLM provider requests
Is CVE-2026-55638 being exploited?
Not confirmed. CVE-2026-55638 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 0.61% probability of exploitation in the next 30 days.
How severe is CVE-2026-55638?
CVE-2026-55638 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-2026-55638?
Yes. A fix has been recorded for CVE-2026-55638. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55638 affect?
CVE-2026-55638 affects 9Router < 0.5.2, Deployments using next.config.mjs rewrite /codex/*, Servers exposing /codex endpoints. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55638?
Upgrade to 9Router v0.5.2 or block /codex routes until patched
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated attacker can bypass API-key gate via /codex/* and force server to call upstream LLM providers using operator credentials, risking credential abuse and data exfiltration.
Immediate action required
- affected< 0.5.2
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.