diff --git a/appengine/flexible/mailgun/requirements.txt b/appengine/flexible/mailgun/requirements.txt
index 23558464899..93d581f7bdf 100644
--- a/appengine/flexible/mailgun/requirements.txt
+++ b/appengine/flexible/mailgun/requirements.txt
@@ -1,3 +1,4 @@
 Flask==1.0.2
 gunicorn==19.9.0
 requests[security]==2.21.0
+urllib3>=2.6.0 # not directly required, pinned by Snyk to avoid a vulnerability