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. (CVE-2026-48521)

Fixed a use-after-free in the ext_authz raw HTTP client where completing an authorization request could destroy the client while its completion handler was still executing. (CVE-2026-50572)

Fixed path matching for paths containing per-segment parameters, where Envoy and backends could select different resources for the same request and bypass path-based selection or authentication. (CVE-2026-73511)

Fixed a use-after-free in the QUIC HTTP datagram handler where late HTTP/3 datagrams could reference a stream decoder that was already destroyed or replaced. (CVE-2026-73512)

Fixed a heap use-after-free where an untrusted upstream could send HTTP/2 response trailers without the END_STREAM flag to an Envoy instance using oghttp2, corrupting stream state and terminating the process. (CVE-2026-73513)

Fixed a stored cross-site scripting issue in the HTML stats interface (/stats?format=html) where dynamically named statistics could introduce attacker-controlled content. (CVE-2026-73546)

Fixed an abnormal process termination in the ext_authz filter when processing CONNECT requests without a :path pseudo-header. (CVE-2026-73547)

Fixed cross-user response poisoning involving generic, non-WebSocket HTTP upgrades, where request payload sent before an upgrade was accepted could contaminate a shared upstream connection. (CVE-2026-73548)

Fixed an abnormal process termination for scoped IPv6 client addresses in original DST clusters with HTTP/3. (CVE-2026-73549)

Fixed an HTTP/2 memory-exhaustion issue where discarded duplicate Host headers were not counted toward request-header size and count limits. (CVE-2026-73550)

Fixed URL normalization of dot and dot-dot path segments containing parameters, which could cause access-control components and upstream applications to interpret a request path differently. (CVE-2026-73551)

Fixed an issue where safe_regex matching treated accepted non-UTF-8 HTTP header bytes as a non-match; in RBAC policies using negative matching this could fail open and allow access to a protected resource. (CVE-2026-73552)

Fixed an authorization bypass when ignore_path_parameters_in_path_matching was enabled, where a path such as /admin;x could bypass an RBAC policy for /admin while still reaching the protected route. (CVE-2026-73553)

The version of ecs-service-connect-agent installed on the remote host is prior to v1.39.1.0-1. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2ECS-2026-137 advisory.

    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. (CVE-2026-48521)

    Fixed a use-after-free in the ext_authz raw HTTP client where completing an authorization request could     destroy the client while its completion handler was still executing. (CVE-2026-50572)

    Fixed path matching for paths containing per-segment parameters, where Envoy and backends could select     different resources for the same request and bypass path-based selection or authentication.
    (CVE-2026-73511)

    Fixed a use-after-free in the QUIC HTTP datagram handler where late HTTP/3 datagrams could reference a     stream decoder that was already destroyed or replaced. (CVE-2026-73512)

    Fixed a heap use-after-free where an untrusted upstream could send HTTP/2 response trailers without the     END_STREAM flag to an Envoy instance using oghttp2, corrupting stream state and terminating the process.
    (CVE-2026-73513)

    Fixed a stored cross-site scripting issue in the HTML stats interface (/stats?format=html) where     dynamically named statistics could introduce attacker-controlled content. (CVE-2026-73546)

    Fixed an abnormal process termination in the ext_authz filter when processing CONNECT requests without a     :path pseudo-header. (CVE-2026-73547)

    Fixed cross-user response poisoning involving generic, non-WebSocket HTTP upgrades, where request payload     sent before an upgrade was accepted could contaminate a shared upstream connection. (CVE-2026-73548)

    Fixed an abnormal process termination for scoped IPv6 client addresses in original DST clusters with     HTTP/3. (CVE-2026-73549)

    Fixed an HTTP/2 memory-exhaustion issue where discarded duplicate Host headers were not counted toward     request-header size and count limits. (CVE-2026-73550)

    Fixed URL normalization of dot and dot-dot path segments containing parameters, which could cause access-     control components and upstream applications to interpret a request path differently. (CVE-2026-73551)

    Fixed an issue where safe_regex matching treated accepted non-UTF-8 HTTP header bytes as a non-match; in     RBAC policies using negative matching this could fail open and allow access to a protected resource.
    (CVE-2026-73552)

    Fixed an authorization bypass when ignore_path_parameters_in_path_matching was enabled, where a path such     as /admin;x could bypass an RBAC policy for /admin while still reaching the protected route.
    (CVE-2026-73553)

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.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2149 advisory.

    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. (CVE-2026-48521)

    Fixed a use-after-free in the ext_authz raw HTTP client where completing an authorization request could     destroy the client while its completion handler was still executing. (CVE-2026-50572)

    Fixed path matching for paths containing per-segment parameters, where Envoy and backends could select     different resources for the same request and bypass path-based selection or authentication.
    (CVE-2026-73511)

    Fixed a use-after-free in the QUIC HTTP datagram handler where late HTTP/3 datagrams could reference a     stream decoder that was already destroyed or replaced. (CVE-2026-73512)

    Fixed a heap use-after-free where an untrusted upstream could send HTTP/2 response trailers without the     END_STREAM flag to an Envoy instance using oghttp2, corrupting stream state and terminating the process.
    (CVE-2026-73513)

    Fixed a stored cross-site scripting issue in the HTML stats interface (/stats?format=html) where     dynamically named statistics could introduce attacker-controlled content. (CVE-2026-73546)

    Fixed an abnormal process termination in the ext_authz filter when processing CONNECT requests without a     :path pseudo-header. (CVE-2026-73547)

    Fixed cross-user response poisoning involving generic, non-WebSocket HTTP upgrades, where request payload     sent before an upgrade was accepted could contaminate a shared upstream connection. (CVE-2026-73548)

    Fixed an abnormal process termination for scoped IPv6 client addresses in original DST clusters with     HTTP/3. (CVE-2026-73549)

    Fixed an HTTP/2 memory-exhaustion issue where discarded duplicate Host headers were not counted toward     request-header size and count limits. (CVE-2026-73550)

    Fixed URL normalization of dot and dot-dot path segments containing parameters, which could cause access-     control components and upstream applications to interpret a request path differently. (CVE-2026-73551)

    Fixed an issue where safe_regex matching treated accepted non-UTF-8 HTTP header bytes as a non-match; in     RBAC policies using negative matching this could fail open and allow access to a protected resource.
    (CVE-2026-73552)

    Fixed an authorization bypass when ignore_path_parameters_in_path_matching was enabled, where a path such     as /admin;x could bypass an RBAC policy for /admin while still reaching the protected route.
    (CVE-2026-73553)

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.

ID	Name	Product	Family	Type	Severity
345786	Amazon Linux 2 : ecs-service-connect-agent (ALASECS-2026-137)	Nessus	Amazon Linux Local Security Checks	Local	high
345777	Amazon Linux 2023 : ecs-service-connect-agent (ALAS2023-2026-2149)	Nessus	Amazon Linux Local Security Checks	Local	high

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CVE-2026-73513

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Tenable Plugins

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high