High severity · published Jul 30, 2026
CVE-2026-18140
Uncontrolled recursion in the aws-smithy-json unknown-key skip path allows unauthenticated remote denial of service in smithy-rs generated servers
7.5
CVSS
0.8%
EPSS
No
On KEV
Description
Uncontrolled recursion in the unknown-key skip path of the aws-smithy-json runtime crate before 0.62.7, which the smithy-rs code generator invokes from every generated struct deserializer, might allow remote unauthenticated users to cause a denial of service (process abort via stack exhaustion) via a single small HTTP request containing deeply nested JSON to a smithy-rs generated server.
To remediate this issue, users should upgrade to aws-smithy-json 0.62.7 or later and rebuild.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 56% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AW
aws-smithy-json · AWS
0.32.0 through 0.62.6 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-18140
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-18140
Vendor Advisory
https://aws.amazon.com/security/security-bulletins/2026-067-aws/
Product
https://crates.io/crates/aws-smithy-json/0.62.7
Vendor Advisory
https://github.com/smithy-lang/smithy-rs/security/advisories/GHSA-8ffr-xgwf-xj56
