Extracted from https://github.com/nodejs/node/pull/66282

diff --git a/src/node_sockaddr.cc b/src/node_sockaddr.cc
index 3f903f548e17..7c2285de32dd 100644
--- a/src/node_sockaddr.cc
+++ b/src/node_sockaddr.cc
@@ -1046,8 +1046,8 @@ bool SocketAddressBlockListWrap::FastCheckString(
   // FastOneByteString is not NUL-terminated. Copy onto the stack
   // before any other work: a GC would invalidate `address`.
   //
-  // uv_ip6_addr only needs the address part (≤39 chars) plus an
-  // optional %zone. A zone longer than UV_IF_NAMESIZE is unknown
+  // uv_ip6_addr only needs the address part (< INET6_ADDRSTRLEN chars)
+  // plus an optional %zone. A zone longer than UV_IF_NAMESIZE is unknown
   // (scope_id 0), same as omitting it. Keep that behavior when the
   // full string does not fit so Fast API and CheckString agree.
   constexpr size_t kMax = INET6_ADDRSTRLEN + UV_IF_NAMESIZE;
@@ -1058,14 +1058,14 @@ bool SocketAddressBlockListWrap::FastCheckString(
   } else if (family == AF_INET6) {
     // uv_ip4_addr rejects %zone. Only IPv6 may drop an overlong zone
     // (unknown zone → scope_id 0, same as uv_ip6_addr).
-    // uv_ip6_addr copies the address part into a 40-byte buffer
-    // (39 chars + NUL). A 40+ char prefix (mixed notation) is
-    // truncated and fails inet_pton — do not keep the full prefix.
+    // uv_ip6_addr copies the address part into an INET6_ADDRSTRLEN
+    // buffer and truncates a longer one to INET6_ADDRSTRLEN - 1 chars
+    // before inet_pton. Do the same so both paths parse the same prefix.
     const char* percent =
         static_cast<const char*>(memchr(address.data, '%', address.length));
     if (percent == nullptr) return false;
-    const size_t addr_len = static_cast<size_t>(percent - address.data);
-    if (addr_len >= 40) return false;
+    size_t addr_len = static_cast<size_t>(percent - address.data);
+    if (addr_len >= INET6_ADDRSTRLEN) addr_len = INET6_ADDRSTRLEN - 1;
     memcpy(buf, address.data, addr_len);
     buf[addr_len] = '\0';
   } else {
diff --git a/test/parallel/test-blocklist.js b/test/parallel/test-blocklist.js
index b0fe4303bfb2..c548917b1c77 100644
--- a/test/parallel/test-blocklist.js
+++ b/test/parallel/test-blocklist.js
@@ -883,12 +883,17 @@ const util = require('util');
   blockList.addAddress('1.1.1.1');
   assert.strictEqual(blockList.check(`1.1.1.1%${'z'.repeat(200)}`), false);
 
-  // Mixed-notation IPv6 is 45 chars. uv_ip6_addr truncates the
-  // address part to 39 when a zone is present, so this is a miss.
+  // Mixed-notation IPv6 is 45 chars. uv_ip6_addr keeps up to
+  // INET6_ADDRSTRLEN - 1 chars of the address part when a zone is
+  // present, so this is a hit on libuv 1.53+.
   const mixed = 'ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255';
   blockList.addAddress(mixed, 'ipv6');
   assert.strictEqual(blockList.check(mixed, 'ipv6'), true);
-  assert.strictEqual(blockList.check(`${mixed}%${'z'.repeat(200)}`, 'ipv6'), false);
+  const isModernLibuv = ((versionString) => {
+    const [major, minor] = versionString.split('.', 2).map(Number);
+    return major >= 1 && minor >= 53;
+  })(process.versions.uv);
+  assert.strictEqual(blockList.check(`${mixed}%${'z'.repeat(200)}`, 'ipv6'), isModernLibuv);
 }
 
 // check() family parameter is case-insensitive.