TLS_RSA_WITH_RC4_128_MD5

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_RSA_WITH_RC4_128_MD5 combines RSA key exchange, RSA authentication, RC4-128 encryption and MD5 integrity protection. Each part is explained below with its known weaknesses; for the bigger picture see how cipher suites work.

Key exchange: RSA key transport. The client picks the premaster secret, encrypts it with the public key in the server certificate (PKCS #1 v1.5 padding) and sends it. There is no ephemeral key, so the suite has no forward secrecy: anyone who records the traffic and later obtains the server's private key can decrypt every past session. The padding is also the target of Bleichenbacher's 1998 chosen-ciphertext attack, and ROBOT (2017) found that many production TLS stacks still leaked that padding oracle, letting an attacker decrypt sessions or sign with the server's key without ever holding it.

Encryption: RC4, a stream cipher whose keystream is measurably biased. AlFardan, Bernstein, Paterson, Poettering and Schuldt showed in 2013 that a secret such as a cookie can be recovered from enough encryptions of it, and RFC 7465 (2015) then prohibited RC4 suites outright: clients MUST NOT offer them and servers MUST NOT select them.

Integrity: HMAC-MD5. MD5 collisions have been practical since 2004; HMAC-MD5 is not directly broken, but MD5 survives only in suites whose ciphers are already obsolete, and RFC 9155 (2021) has since removed MD5 from TLS 1.2 signatures too.

Why this rating

ssl.sh rating: Insecure. The reasons:

• Uses RC4, which RFC 7465 prohibits in all TLS versions because of practical biases in its keystream.
• Uses HMAC-MD5 for integrity; MD5 is broken and these suites are deprecated.

How ssl.sh rates cipher suites

Which TLS libraries support it

Support for TLS_RSA_WITH_RC4_128_MD5 as read from each library's own source code or official documentation on 2026-11-10. “Enabled by default” means the library negotiates it with no configuration; “off by default” means it is implemented but has to be switched on.

Enabled by default in 1 of the 9 libraries tracked here: NSS 3.133. Supported but off by default in: Java 21 (SunJSSE) and Windows Schannel (Windows 11 / Server 2022). Also implemented by: OpenSSL 3.5 and GnuTLS.

NSS shows the library's own defaults; Firefox switches every NSS suite off at start-up and re-enables only those with a security.ssl3.* or security.tls13.* preference. Java defaults are derived from the jdk.tls.disabledAlgorithms value Oracle documents for JDK 21, which later updates may extend. The OpenSSL and GnuTLS rows only show whether the suite is implemented.

History and standards status

TLS_RSA_WITH_RC4_128_MD5 (0x00,0x04) is registered in the IANA TLS Cipher Suites registry with RFC 5246, “The Transport Layer Security (TLS) Protocol Version 1.2” (August 2008, Standards Track) as its specification. RFC 5246 has since been obsoleted by RFC 8446 (2018) and RFC 9846 (2026). DTLS 1.2 (RFC 6347, January 2012) had already said RC4 MUST NOT be used with DTLS. RFC 7465 (2015) prohibits RC4 cipher suites in every TLS version: clients MUST NOT offer them and servers MUST NOT select them. RFC 9325 (2022), part of BCP 195, says implementations SHOULD NOT negotiate static RSA key transport (TLS_RSA_WITH_*) because it lacks forward secrecy. RFC 10015 (2026) now says clients MUST NOT offer and servers MUST NOT select RSA key-exchange suites in (D)TLS 1.2, and IANA changed this entry's Recommended value to D.

Enable or disable it in Nginx and Apache

This suite is rated insecure, so we don't show how to enable it. Make sure it's excluded.

Disable

Either leave the suite out of your list or exclude it explicitly with a leading "!". Reload the server afterwards (nginx -s reload, apachectl graceful).

# Nginx
ssl_ciphers 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:!RC4-MD5';

# Apache httpd (mod_ssl)
SSLCipherSuite ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:!RC4-MD5

How to test whether a server accepts it

Offer only TLS_RSA_WITH_RC4_128_MD5 with openssl s_client; if the handshake completes, the server accepts it:

openssl s_client -connect example.com:443 -tls1_2 -cipher RC4-MD5 </dev/null

If the handshake succeeds, the server accepts the suite; "no cipher match" or a handshake failure means it doesn't.

nmap's ssl-enum-ciphers script connects repeatedly, trying one suite at a time, and lists every suite the server accepts with a grade from A to F. Look for TLS_RSA_WITH_RC4_128_MD5 in its output:

nmap --script ssl-enum-ciphers -p 443 example.com

To decode a name or hex code, use the cipher suite lookup; the SSL checker shows which protocol versions a live server accepts and the cipher suite it negotiates.