CVE-2026-18140
Remote DoS via recursive JSON in aws-smithy-json (<0.62.7) crashing smithy-rs servers.
Is CVE-2026-18140 being exploited?
Not confirmed. CVE-2026-18140 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-2026-18140?
CVE-2026-18140 is rated High with a CVSS score of 8.7. 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-2026-18140?
Yes. A fix has been recorded for CVE-2026-18140. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-18140 affect?
CVE-2026-18140 affects aws-smithy-json <0.62.7, smithy-rs generated servers, Any service using aws-smithy-json runtime. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-18140?
Upgrade aws-smithy-json to >=0.62.7, rebuild and redeploy affected services.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote unauthenticated attacker can crash servers (stack exhaustion/process abort) with one deeply nested JSON request.
Immediate action required
- affected>= 0.32.0 and <= 0.62.6
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.