Amazon Linux 2 : ecs-service-connect-agent, --advisory ALAS2ECS-2026-100 (ALASECS-2026-100)

high Nessus Plugin ID 304587

Synopsis

The remote Amazon Linux 2 host is missing a security update.

Description

The version of ecs-service-connect-agent installed on the remote host is prior to v1.34.13.0-1. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2ECS-2026-100 advisory.

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies--specifically Deny rules--by sending duplicate headers, effectively obscuring the malicious value from exact-match mechanisms. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13. (CVE-2026-26308)

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, an off-by-one write in Envoy::JsonEscaper::escapeString() can corrupt std::string null-termination, causing undefined behavior and potentially leading to crashes or out-of-bounds reads when the resulting string is later treated as a C-string. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.
(CVE-2026-26309)

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, calling Utility::getAddressWithPort with a scoped IPv6 addresses causes a crash. This utility is called in the data plane from the original_src filter and the dns filter. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13. (CVE-2026-26310)

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, a logic vulnerability in Envoy's HTTP connection manager (FilterManager) that allows for Zombie Stream Filter Execution. This issue creates a Use-After-Free (UAF) or state-corruption window where filter callbacks are invoked on an HTTP stream that has already been logically reset and cleaned up. The vulnerability resides in source/common/http/filter_manager.cc within the FilterManager::decodeData method.
The ActiveStream object remains valid in memory during the deferred deletion window. If a DATA frame arrives on this stream immediately after the reset (e.g., in the same packet processing cycle), the HTTP/2 codec invokes ActiveStream::decodeData, which cascades to FilterManager::decodeData.
FilterManager::decodeData fails to check the saw_downstream_reset_ flag. It iterates over the decoder_filters_ list and invokes decodeData() on filters that have already received onDestroy(). This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13. (CVE-2026-26311)

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, At the rate limit filter, if the response phase limit with apply_on_stream_done in the rate limit configuration is enabled and the response phase limit request fails directly, it may crash Envoy. When both the request phase limit and response phase limit are enabled, the safe gRPC client instance will be re-used for both the request phase request and response phase request. But after the request phase request is done, the inner state of the request phase limit request in gRPC client is not cleaned up. When a second limit request is sent at response phase, and the second limit request fails directly, the previous request's inner state may be accessed and result in crash. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13. (CVE-2026-26330)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Run 'yum update ecs-service-connect-agent' or or 'yum update --advisory ALAS2ECS-2026-100' to update your system.

Plugin Details

Severity: High

ID: 304587

File Name: al2_ALASECS-2026-100.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 4/1/2026

Updated: 4/1/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5.0

CVSS v2

Risk Factor: High

Base Score: 8.5

Temporal Score: 6.7

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:P/A:N

CVSS Score Source: CVE-2026-26308

CVSS v3

Risk Factor: High

Base Score: 8.2

Temporal Score: 7.4

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:amazon:linux:ecs-service-connect-agent, cpe:/o:amazon:linux:2

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 4/1/2026

Vulnerability Publication Date: 3/10/2026

Reference Information

CVE: CVE-2026-26308, CVE-2026-26309, CVE-2026-26310, CVE-2026-26311, CVE-2026-26330

Detections

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