diff --git a/mailbox-app/requirements/constraints.txt b/mailbox-app/requirements/constraints.txt
index c8bb3fe..11cd7a4 100644
--- a/mailbox-app/requirements/constraints.txt
+++ b/mailbox-app/requirements/constraints.txt
@@ -1,6 +1,6 @@
 # Runtime and verification constraints for reproducible builds.
 argon2-cffi==25.1.0
-argon2-cffi-bindings==25.1.0
+argon2-cffi-bindings==26.1.0
 asgiref==3.11.1
 bandit==1.9.4
 bleach==6.4.0
diff --git a/mailbox-app/requirements/locked.txt b/mailbox-app/requirements/locked.txt
index 8cf762b..49462b8 100644
--- a/mailbox-app/requirements/locked.txt
+++ b/mailbox-app/requirements/locked.txt
@@ -1,6 +1,6 @@
 # Fully pinned production dependency lock generated from the verified runtime environment.
 argon2-cffi==25.1.0
-argon2-cffi-bindings==25.1.0
+argon2-cffi-bindings==26.1.0
 asgiref==3.11.1
 bleach==6.4.0
 cffi==2.0.0