diff --git a/docs/doc-requirements.txt b/docs/doc-requirements.txt
index bb439ddcf2..4c1f4788d1 100644
--- a/docs/doc-requirements.txt
+++ b/docs/doc-requirements.txt
@@ -3,3 +3,4 @@ sphinx-rtd-theme
 nbsphinx
 sphinxcontrib_github_alt
 myst_parser
+tornado>=6.5.5 # not directly required, pinned by Snyk to avoid a vulnerability