diff --git a/.cargo/config.toml b/.cargo/config.toml
index aa777fd804..b6a73fead8 100644
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -42,6 +42,7 @@ tree --no-default-features --depth 1 --edges=features,normal
 # - RUSTSEC-2024-0370: Unmaintained transitive dependency. Only affects macro generation efficiency.
 # - RUSTSEC-2024-0388: Unmaintained transitive dependency `derivative` used by substrate.
 # - RUSTSEC-2024-0384: Unmaintained transitive dependency `instant` used by substrate.
+# - RUSTSEC-2024-0421: Transitive dependency `idna` used by libp2p, among others.
 cf-audit = '''
 audit -D unmaintained -D unsound
     --ignore RUSTSEC-2021-0139
@@ -53,4 +54,5 @@ audit -D unmaintained -D unsound
     --ignore RUSTSEC-2024-0370
     --ignore RUSTSEC-2024-0388
     --ignore RUSTSEC-2024-0384
+    --ignore RUSTSEC-2024-0421
 '''