EUVD-2026-51271Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Remote unauthenticated JSON parsing with no interaction gives AV:N/AC:L/PR:N/UI:N; a stack-exhaustion abort is availability-only, so C:N/I:N/A:H with scope unchanged.
Primary rating from Vendor (AMZN).
CVSS VectorVendor: AMZN
Lifecycle Timeline
5DescriptionCVE.org
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.
AnalysisAI
Denial of service in the aws-smithy-json Rust runtime crate (versions before 0.62.7) lets remote unauthenticated attackers abort a process via stack exhaustion. Because the smithy-rs code generator wires this crate's deserializer into every generated struct, any smithy-rs generated server that parses JSON is exposed, and a single small HTTP request carrying deeply nested JSON triggers uncontrolled recursion in the unknown-key skip path. No public exploit was identified at time of analysis and the flaw is not in CISA KEV, but the trigger is trivial and a vendor patch is available.
Technical ContextAI
The affected component is aws-smithy-json, part of the smithy-rs runtime that underpins AWS's Smithy-generated Rust clients and servers (CPE cpe:2.3:a:aws:aws-smithy-json). Smithy is AWS's interface definition language; its Rust code generator emits per-shape deserializers that delegate JSON token handling to this crate. The root cause is CWE-674 (Uncontrolled Recursion): when the parser encounters an object key it does not recognize, its skip-value routine recurses through nested structures without a depth limit. Deeply nested JSON therefore drives native stack growth until the Rust runtime hits its stack guard and aborts the process, rather than returning a bounded parse error.
RemediationAI
Vendor-released patch: aws-smithy-json 0.62.7. Upgrade the crate to 0.62.7 or later (published at https://crates.io/crates/aws-smithy-json/0.62.7) by running cargo update -p aws-smithy-json, confirming the resolved version in Cargo.lock, then rebuilding and redeploying - because this is a compiled dependency, updating the lockfile without a rebuild does not remediate. Review the AWS bulletin (https://aws.amazon.com/security/security-bulletins/2026-067-aws/) and the GHSA advisory (https://github.com/smithy-lang/smithy-rs/security/advisories/GHSA-8ffr-xgwf-xj56). Where an immediate rebuild is impossible, front smithy-rs generated servers with a reverse proxy or API gateway and reject requests whose JSON exceeds a modest nesting depth; the trade-off is that legitimately deep valid payloads may be dropped, and a byte-size cap alone is weak because the exploit payload is small, so prefer an explicit depth limit. Process supervision with automatic restart shortens the outage from any successful abort but does not prevent it.
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Same weakness CWE-674 – Uncontrolled Recursion
View allSame technique Denial Of Service
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