CVE-2026-15957
smithy-rs deserializers allow remote DoS via deeply nested JSON/CBOR/XML.
Is CVE-2026-15957 being exploited?
Not confirmed. CVE-2026-15957 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 0.75% probability of exploitation in the next 30 days.
How severe is CVE-2026-15957?
CVE-2026-15957 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-2026-15957?
Yes. A fix has been recorded for CVE-2026-15957. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-15957 affect?
CVE-2026-15957 affects aws-sdk-rust (versions before release-2026-06-02), smithy-rs code-generated servers (before release-2026-06-01), Custom services using smithy-rs codegen. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-15957?
Upgrade aws-sdk-rust to release-2026-06-02+ and regenerate smithy-rs servers with release-2026-06-01+.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote denial-of-service: stack exhaustion/process abort when parsing deeply nested JSON, CBOR, or XML in generated clients/servers.
Immediate action required
- affected< release-2026-06-02
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.