diff --git a/requirements-dev.txt b/requirements-dev.txt
index ea38712d89d..31fd0912a63 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -16,3 +16,4 @@ lintrunner-adapters>=0.12.3
 # Edit additional linter dependencies in requirements-lintrunner.txt
 # Dependencies for the reference implementation.
 -r requirements-reference.txt
+tornado>=6.4.2 # not directly required, pinned by Snyk to avoid a vulnerability