# TLS_RSA_WITH_NULL_SHA256 cipher suite

> TLS_RSA_WITH_NULL_SHA256 (0x00,0x3B): RSA/RSA · NULL · TLS 1.2. ssl.sh rating: Insecure. OpenSSL/GnuTLS names and Nginx/Apache config.

Source: https://ssl.sh/ciphers/tls-rsa-with-null-sha256/
Last updated: 2026-11-10

TLS_RSA_WITH_NULL_SHA256 (0x00,0x3B) is a cipher suite for TLS 1.2: RSA key exchange, RSA authentication, NULL encryption and SHA256 message authentication. ssl.sh rates it Insecure.

| Field | Value |
|---|---|
| IANA | TLS_RSA_WITH_NULL_SHA256 |
| Hex code | 0x00,0x3B |
| OpenSSL | NULL-SHA256 |
| GnuTLS | TLS_RSA_NULL_SHA256 |
| Key exchange | RSA |
| Authentication | RSA |
| Encryption | NULL |
| MAC | SHA256 |
| TLS versions | TLS 1.2 |
| Rating | Insecure |
| IANA "Recommended" | D |
| References | RFC 5246, RFC 10015 |

## What each component means

A [cipher suite](https://ssl.sh/glossary/cipher-suite/) names the algorithms a client and server agree on in one handshake. TLS_RSA_WITH_NULL_SHA256 combines RSA key exchange, RSA authentication, NULL encryption and SHA256 integrity protection. Each part is explained below with its known weaknesses; for the bigger picture see [how cipher suites work](https://ssl.sh/learn/cipher-suites/).

Key exchange: [RSA](https://ssl.sh/glossary/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](https://ssl.sh/glossary/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](https://ssl.sh/glossary/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: none. Records are only protected by the SHA256 MAC, so anyone on the path can read the plaintext. [RFC 9325](https://www.rfc-editor.org/rfc/rfc9325) (2022) says implementations MUST NOT negotiate NULL-encryption suites, while noting they can still be useful for testing and debugging.

Integrity: HMAC-SHA256 over each record, computed before encryption (MAC-then-encrypt). In TLS 1.2 the SHA256 in the name also selects the PRF hash. Because of that, the suite needs TLS 1.2 and cannot be used with older versions.

## Why this rating

- No encryption (NULL cipher): traffic is sent in clear text.

## Which TLS libraries support it

Support for TLS_RSA_WITH_NULL_SHA256 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.

| Library | Status | Details |
|---|---|---|
| OpenSSL 3.5 | Implemented | cipher string `NULL-SHA256` |
| GnuTLS | Implemented | name `TLS_RSA_NULL_SHA256`; minimum protocol `TLS 1.2` |
| BoringSSL | Not supported | - |
| Go crypto/tls | Not supported | - |
| NSS 3.133 | Supported, off by default | NSS library default |
| Firefox | Not supported | - |
| Java 21 (SunJSSE) | Supported, off by default | blocked by “`NULL`” in the default jdk.tls.disabledAlgorithms |
| Windows Schannel (Windows 11 / Server 2022) | Supported, off by default | only used when the application explicitly requests it; filtered out when the application sets SCH_USE_STRONG_CRYPTO |
| rustls 0.23.46 | Not supported | - |

None of the 9 libraries tracked here enables it by default. Supported but off by default in: NSS 3.133, 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.

- [BoringSSL — ssl/ssl_cipher.cc (main)](https://boringssl.googlesource.com/boringssl/+/refs/heads/main/ssl/ssl_cipher.cc) (2026-11-10)
- [Go — src/crypto/tls/cipher_suites.go (master)](https://github.com/golang/go/blob/master/src/crypto/tls/cipher_suites.go) (2026-11-10)
- [Go — src/crypto/tls/defaults.go (master)](https://github.com/golang/go/blob/master/src/crypto/tls/defaults.go) (2026-11-10)
- [NSS — lib/ssl/ssl3con.c (as vendored in Firefox)](https://github.com/mozilla-firefox/firefox/blob/main/security/nss/lib/ssl/ssl3con.c) (2026-11-10)
- [NSS — TAG-INFO](https://github.com/mozilla-firefox/firefox/blob/main/security/nss/TAG-INFO) (2026-11-10)
- [Firefox — security/manager/ssl/nsNSSComponent.cpp](https://github.com/mozilla-firefox/firefox/blob/main/security/manager/ssl/nsNSSComponent.cpp) (2026-11-10)
- [Firefox — modules/libpref/init/StaticPrefList.yaml](https://github.com/mozilla-firefox/firefox/blob/main/modules/libpref/init/StaticPrefList.yaml) (2026-11-10)
- [Oracle — JDK 21 Providers Documentation: SunJSSE Cipher Suites](https://docs.oracle.com/en/java/javase/21/security/oracle-providers.html#GUID-7093246A-31A3-4304-AC5F-5FB6400405E2) (2026-11-10)
- [Oracle — JDK 21 JSSE Reference Guide: jdk.tls.disabledAlgorithms](https://docs.oracle.com/en/java/javase/21/security/java-secure-socket-extension-jsse-reference-guide.html) (2026-11-10)
- [Microsoft Learn — TLS Cipher Suites in Windows 11](https://learn.microsoft.com/en-us/windows/win32/secauthn/tls-cipher-suites-in-windows-11) (2026-11-10)
- [Microsoft Learn — TLS Cipher Suites in Windows Server 2022](https://learn.microsoft.com/en-us/windows/win32/secauthn/tls-cipher-suites-in-windows-server-2022) (2026-11-10)
- [docs.rs — rustls 0.23.46 crypto::aws_lc_rs (default provider)](https://docs.rs/rustls/0.23.46/src/rustls/crypto/aws_lc_rs/mod.rs.html) (2026-11-10)

## History and standards status

TLS_RSA_WITH_NULL_SHA256 (0x00,0x3B) is registered in the IANA TLS Cipher Suites registry with [RFC 5246](https://www.rfc-editor.org/rfc/rfc5246), “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](https://www.rfc-editor.org/rfc/rfc8446) (2018) and [RFC 9846](https://www.rfc-editor.org/rfc/rfc9846) (2026). [RFC 9325](https://www.rfc-editor.org/rfc/rfc9325) (2022), part of BCP 195, says implementations MUST NOT negotiate suites with NULL encryption. [RFC 9325](https://www.rfc-editor.org/rfc/rfc9325) (2022), part of BCP 195, says implementations SHOULD NOT negotiate static RSA key transport (TLS_RSA_WITH_*) because it lacks forward secrecy. [RFC 10015](https://www.rfc-editor.org/rfc/rfc10015) (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.

## Nginx / Apache

Disable

```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:!NULL-SHA256';
```

```apache
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:!NULL-SHA256
```


## How to test whether a server accepts it

Offer only TLS_RSA_WITH_NULL_SHA256 with openssl s_client; if the handshake completes, the server accepts it:

```bash
openssl s_client -connect example.com:443 -tls1_2 -cipher NULL-SHA256 </dev/null
```

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_NULL_SHA256 in its output:

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

To decode a name or hex code, use the [cipher suite lookup](https://ssl.sh/tools/cipher-suite-lookup/); the [SSL checker](https://ssl.sh/tools/ssl-checker/) shows which protocol versions a live server accepts and the cipher suite it negotiates.

## FAQ

### Is TLS_RSA_WITH_NULL_SHA256 secure?

No. ssl.sh rates it insecure. No encryption (NULL cipher): traffic is sent in clear text. [RFC 10015](https://www.rfc-editor.org/rfc/rfc10015) (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.

### Can TLS_RSA_WITH_NULL_SHA256 be used with TLS 1.3?

No. TLS 1.3 has its own suites that name only the AEAD and the hash, and TLS 1.2 suites can't be used in a TLS 1.3 handshake. TLS_RSA_WITH_NULL_SHA256 works with TLS 1.2. The closest TLS 1.3 suite is [TLS_AES_128_GCM_SHA256](https://ssl.sh/ciphers/tls-aes-128-gcm-sha256/), which TLS 1.3 combines with a separately negotiated key exchange such as X25519.

### How do I disable TLS_RSA_WITH_NULL_SHA256 in Nginx or Apache?

Exclude it by its OpenSSL name: append `!NULL-SHA256` to `ssl_ciphers` in Nginx or to `SSLCipherSuite` in Apache httpd. Listing only the suites you want, as in the snippet above, works even better. Reload the server and repeat the openssl s_client test to confirm the handshake now fails.

### Which clients and libraries still support TLS_RSA_WITH_NULL_SHA256?

Only after explicit configuration: NSS 3.133, Java 21 (SunJSSE) and Windows Schannel (Windows 11 / Server 2022). Implemented, default state not tracked here: OpenSSL 3.5 and GnuTLS. Not supported: BoringSSL, Go crypto/tls, Firefox and rustls 0.23.46.