Amazon Linux 2 (EOS) Security Advisory: ALAS2-2026-3925
Advisory Released Date: 2026-09-28
Advisory Updated Date: 2026-09-28
Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.8, Tornado parses application/x-www-form-urlencoded request bodies with urllib.parse.parse_qs in tornado/escape.py without passing max_num_fields. RequestHandler._execute in tornado/web.py parses the body before handler dispatch through HTTPServerRequest._parse_body and parse_body_arguments in tornado/httputil.py, so an unauthenticated request body containing millions of separator-delimited fields can synchronously stall the single-threaded event loop and delay every connection. The body is bounded only by max_buffer_size, which defaults to 104857600 bytes. This issue is fixed in version 6.5.8. (CVE-2026-82397)
Affected Packages:
python-tornado
Note:
This advisory is applicable to Amazon Linux 2 (AL2) Core repository. Visit this FAQ section for the difference between AL2 Core and AL2 Extras advisories.
Issue Correction:
Run yum update python-tornado or yum update --advisory ALAS2-2026-3925 to update your system.
aarch64:
python-tornado-4.2.1-3.amzn2.0.7.aarch64
python-tornado-doc-4.2.1-3.amzn2.0.7.aarch64
python-tornado-debuginfo-4.2.1-3.amzn2.0.7.aarch64
i686:
python-tornado-4.2.1-3.amzn2.0.7.i686
python-tornado-doc-4.2.1-3.amzn2.0.7.i686
python-tornado-debuginfo-4.2.1-3.amzn2.0.7.i686
src:
python-tornado-4.2.1-3.amzn2.0.7.src
x86_64:
python-tornado-4.2.1-3.amzn2.0.7.x86_64
python-tornado-doc-4.2.1-3.amzn2.0.7.x86_64
python-tornado-debuginfo-4.2.1-3.amzn2.0.7.x86_64