Amazon Linux 2 (EOS) Security Advisory: ALAS2ECS-2026-149
Advisory Released Date: 2026-10-24
Advisory Updated Date: 2026-10-26
When "Trailer" headers are sent by a client, the HTTP server internally uses the header values to populate the Request.Trailer map passed to the server handler. Because Request.Trailer is a map, each entry incurs memory overhead. For HTTP/2 servers, a malicious client can exploit this by sending a "Trailer" header that declares a large number of fields causing the server to allocate a disproportionate amount of memory while bypassing Server.MaxHeaderValueCount and Server.MaxHeaderBytes limits.
This exploit is not applicable for HTTP/1 servers, which do not support multiplexing a large number of requests over one TCP connection, and whose Server.MaxHeaderBytes are calculated differently.
Server.MaxHeaderValueCount and Server.MaxHeaderBytes limits are now applied towards the trailer fields declared in "Trailer" headers.
NOTE: https://www.openwall.com/lists/oss-security/2026/10/08/9
NOTE: https://github.com/golang/go/issues/81857
NOTE: Fixed by: https://github.com/golang/go/commit/cbb0fb8b51cba866018b8a0fb4b5458f16c5c80b (go1.27.2)
NOTE: Fixed by: https://github.com/golang/go/commit/6e049521882c944afc1e519a83971ec421dc2974 (go1.26.9) (CVE-2026-78659)
Affected Packages:
ecs-init
Note:
This advisory is applicable to Amazon Linux 2 - Ecs Extra. Visit this page to learn more about Amazon Linux 2 (AL2) Extras and this FAQ section for the difference between AL2 Core and AL2 Extras advisories.
Issue Correction:
Run yum update ecs-init or yum update --advisory ALAS2ECS-2026-149 to update your system.
aarch64:
ecs-init-1.108.1-1.amzn2.aarch64
src:
ecs-init-1.108.1-1.amzn2.src
x86_64:
ecs-init-1.108.1-1.amzn2.x86_64