# CVE-2026-48521: ecs-service-connect-agent: An Envoy proxy handling HTTP/3 connections can dereference a null transport socket option during the selection of a c...

CVE-2026-48521 is fixed in ecs-service-connect-agent on 1 platform by ALAS2023-2026-2149 (version v1.39.1.0-1.amzn2023), released September 14, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-48521
- Priority: High
- CVSS: n/a (important)
- EPSS: 0.0074
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 14, 2026

## Description

An Envoy proxy handling HTTP/3 connections can dereference a null transport socket option during the selection of a connection pool. This null pointer dereference is a CWE-476 flaw that may cause the process to crash or terminate unexpectedly, leading to a denial of service for the services routed through the affected Envoy instance. The vulnerability is triggered when a client initiates an HTTP/3 session that exercises the connection-pool selection logic, which may provide the attacker a remote execution path to disrupt the proxy.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | ecs-service-connect-agent amzn 2023 | v1.39.1.0-1.amzn2023 | [ALAS2023-2026-2149](https://patchblox.com/security/data/fix/linux/alas2023-2026-2149.md) | Sep 14, 2026 |

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Data as of 2026-11-11T13:47:35Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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