TLS_RSA_EXPORT_WITH_DES40_CBC_SHA

What each component means

A cipher suite names the algorithms a client and server agree on in one handshake. TLS_RSA_EXPORT_WITH_DES40_CBC_SHA combines RSA key exchange, RSA authentication, DES40-CBC encryption and SHA1 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.

This is a 1990s EXPORT suite, built for US export rules that capped encryption at 40 bits and RSA key exchange at 512 bits. FREAK (CVE-2015-0204, March 2015) showed that a man-in-the-middle could make vulnerable clients, OpenSSL and Apple's Secure Transport among them, accept a 512-bit export RSA key even when they had not offered an export suite; such keys could be factored in hours on rented cloud servers.

Encryption: DES reduced to 40 bits of secret key, an export-grade cipher that ordinary hardware brute-forces quickly. RFC 9325 (2022) forbids any suite with less than 112 bits of security and names export-level 40- and 56-bit ciphers explicitly.

Mode: CBC with MAC-then-encrypt. TLS 1.2 and earlier compute the HMAC over the plaintext, then pad and encrypt, so a receiver has to decrypt before it can check integrity. That ordering produced a long run of padding-oracle attacks: BEAST (CVE-2011-3389) against TLS 1.0's predictable IVs, Lucky Thirteen (CVE-2013-0169, 2013), which times the MAC check, and POODLE (CVE-2014-3566, 2014) against SSL 3.0's unchecked padding. RFC 9325 (2022) says CBC suites SHOULD NOT be used unless the encrypt_then_mac extension (RFC 7366) is also negotiated.

Integrity: HMAC-SHA1. SHA-1 collisions are practical (SHAttered, 2017), but HMAC does not rely on collision resistance, so HMAC-SHA1 record MACs are not considered broken; this suite's weak points lie elsewhere.

Why this rating

ssl.sh rating: Insecure. The reasons:

• Export-grade cryptography (40/56-bit keys), broken since the 1990s and exploited by FREAK and Logjam.
• Uses single DES, whose 56-bit key can be brute-forced; RFC 5246 removed DES suites from TLS 1.2.

How ssl.sh rates cipher suites

Which TLS libraries support it

Support for TLS_RSA_EXPORT_WITH_DES40_CBC_SHA 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.

None of the 9 libraries tracked here enables it by default. Supported but off by default in: Java 21 (SunJSSE).

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_EXPORT_WITH_DES40_CBC_SHA (0x00,0x08) is registered in the IANA TLS Cipher Suites registry with RFC 4346, “The Transport Layer Security (TLS) Protocol Version 1.1” (April 2006, Historic) as its specification. RFC 4346 has since been obsoleted by RFC 5246 (2008). As early as 2006, the TLS 1.1 specification RFC 4346 said TLS 1.1 implementations MUST NOT negotiate the export suites, which include this one. It can only be negotiated in SSL 3.0, TLS 1.0. RFC 7568 (2015) deprecated SSL 3.0 and RFC 8996 (2021) deprecated TLS 1.0 and TLS 1.1, so no protocol version still in good standing allows it. 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

OpenSSL 3.5 doesn't implement this suite, so stock Nginx and Apache httpd builds can't offer it and you don't need to disable it.

How to test whether a server accepts it

OpenSSL 3.5 cannot offer TLS_RSA_EXPORT_WITH_DES40_CBC_SHA, so openssl s_client can't test it directly; use a scanner that implements the suite itself.

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_EXPORT_WITH_DES40_CBC_SHA 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.