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s2n-quic CVE-2026-94450

| EUVDEUVD-2026-84822 HIGH
Improper Validation of Specified Quantity in Input (CWE-1284)
2026-09-22 AMZN
8.7
CVSS 4.0 · Vendor: AMZN
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Severity by source

Vendor (AMZN) PRIMARY
8.7 HIGH
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
vuln.today AI
7.5 HIGH

Unauthenticated single-datagram network DoS (AV:N/AC:L/PR:N/UI:N); the Retry-config prerequisite is a deployment gate not modeled in base metrics; availability-only impact (A:H, C/I:N).

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (AMZN).

CVSS VectorVendor: AMZN

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

7
POC Analysis Generated
Sep 22, 2026 - 23:21 vuln.today
Metadata Corrected
Sep 22, 2026 - 21:40 vuln.today
tag: Rust added
Analysis Updated
Sep 22, 2026 - 21:28 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Sep 22, 2026 - 21:22 vuln.today
cvss_changed
CVSS changed
Sep 22, 2026 - 21:22 NVD
7.5 (HIGH) 8.7 (HIGH)
Analysis Generated
Sep 22, 2026 - 21:01 vuln.today
CVE Published
Sep 22, 2026 - 20:04 cve.org
HIGH 7.5

DescriptionCVE.org

Improper validation of the Destination Connection ID length in s2n-quic 1.88.0 and earlier may allow an unauthenticated remote user to cause a denial of service by shutting down a server endpoint via a single crafted UDP datagram. Only server endpoints specifically configured to send Retry packets are affected.

To remediate this issue, users should upgrade to version v1.89.0 or later.

AnalysisAI

Denial of service in AWS s2n-quic 1.88.0 and earlier allows an unauthenticated remote attacker to shut down a QUIC server endpoint by sending a single crafted UDP datagram that carries a Destination Connection ID of invalid length, which the library fails to validate properly. The impact is limited to server endpoints specifically configured to send QUIC Retry packets (servers that never emit Retry packets are not affected), and the CVSS:3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) confirms a full availability loss with no confidentiality or integrity impact and no authentication or user interaction required. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Execution
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Impact
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Vulnerability AssessmentAI

Exploitation Exploitable only against s2n-quic server endpoints (version ≤1.88.0) that are specifically configured to send QUIC Retry packets - servers not using Retry are not affected. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment All available signals point to a genuine but narrowly-scoped availability issue rather than a top-priority emergency. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade to s2n-quic v1.89.0 or later, which is the vendor-released fix referenced at https://github.com/aws/s2n-quic/releases/tag/v1.89.0; the same guidance is published in AWS security bulletin 2026-116-aws (https://aws.amazon.com/security/security-bulletins/2026-116-aws/) and advisory GHSA-5rw2-6x5m-v22x. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, inventory all AWS s2n-quic deployments and dependencies to identify instances running v1.88.0 or earlier, prioritizing internet-facing QUIC servers configured to emit Retry packets, and confirm whether those endpoints are exposed to untrusted UDP traffic. …

Sign in for detailed remediation steps and compensating controls.

Threat intelligence, references, and detailed analysis are available after sign-in.

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CVE-2026-94450 vulnerability details – vuln.today

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