diff --git a/requirements.txt b/requirements.txt
index c520b8542..1fca607e7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -44,6 +44,7 @@ cryptography
 ### git+https://github.com/crim-ca/cwltool@docker-gpu#egg=cwltool
 ##cwltool==3.1.20230906142556
 cwltool @ git+https://github.com/fmigneault/cwltool.git@fix-load-contents-array
+dnspython>=2.6.1  # not directly required, pinned by Snyk to avoid a vulnerability; via pymongo dependency
 docker>=7.1
 duration
 esgf-compute-api @ git+https://github.com/ESGF/esgf-compute-api.git@v2.3.7