# What Is SSL 3.0 (SSLv3, Secure Sockets Layer 3.0)?

> SSL 3.0 is the last version of Netscape's Secure Sockets Layer protocol, released in 1996, broken by POODLE in 2014 and deprecated by RFC 7568 in 2015.

Source: https://ssl.sh/glossary/ssl-3-0/
Last updated: 2026-11-10

SSL 3.0 is the final version of the Secure Sockets Layer protocol designed at Netscape, released in 1996 and later documented as the historic RFC 6101. It became the basis for [TLS 1.0](https://ssl.sh/glossary/tls-1-0/), and its record layer and handshake shape survive in every later TLS version.

## Why it matters
In October 2014 the [POODLE](https://ssl.sh/glossary/poodle/) attack showed that SSL 3.0's CBC padding cannot be secured: the padding bytes are not covered by the MAC and their content is unspecified, so an attacker who can make a client repeat requests can recover secrets such as cookies byte by byte. The only non-CBC alternative in SSL 3.0 was RC4, itself broken and later prohibited by RFC 7465, which left no safe configuration. Because many clients used to retry failed handshakes with lower versions, an attacker could force a [downgrade](https://ssl.sh/glossary/downgrade-attack/) to SSL 3.0 even when both sides supported TLS. [RFC 7568](https://www.rfc-editor.org/rfc/rfc7568) deprecated SSL 3.0 in June 2015.

## Example
Confirm that a server no longer offers SSLv3:

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

The output should contain no SSLv3 section. Most current OpenSSL builds cannot even attempt an SSL 3.0 handshake.

## Common misconceptions
- **"An 'SSL certificate' means the site uses SSL."** Certificates are independent of the protocol version. Sites with "SSL certificates" today negotiate TLS 1.2 or 1.3.
- **"POODLE only affects clients that prefer SSL 3.0."** An active attacker could trigger the fallback, which is why servers had to disable SSL 3.0 entirely; TLS_FALLBACK_SCSV (RFC 7507) was added to block such forced downgrades.
- **"SSL 3.0 is acceptable with RC4."** RC4 has its own exploitable biases, so neither SSL 3.0 option is safe.

## Related terms

- [SSL](https://ssl.sh/zh/glossary/ssl/): SSL 是 Netscape 在上世纪 90 年代设计的加密传输协议，已被 TLS 完全取代，如今“SSL”多半只是 TLS 和证书的习惯叫法。
- [TLS](https://ssl.sh/zh/glossary/tls/): TLS 是 IETF 制定的传输层安全协议，为 HTTPS 等网络连接提供加密、完整性保护和服务器身份认证，是 SSL 的继任者。
- [TLS 1.0](https://ssl.sh/zh/glossary/tls-1-0/): TLS 1.0 是传输层安全协议的第一个版本，1999 年以 RFC 2246 发布，2021 年被 RFC 8996 正式废弃，主流浏览器已不再支持。
- [POODLE](https://ssl.sh/zh/glossary/poodle/): POODLE 是 2014 年公布的攻击（CVE-2014-3566），利用 SSL 3.0 不校验 CBC 填充的缺陷，从加密连接中逐字节还原 Cookie 等秘密。
- [降级攻击](https://ssl.sh/zh/glossary/downgrade-attack/): 降级攻击是指攻击者迫使客户端和服务器协商出比双方实际支持的更旧的协议版本或更弱的算法，从而利用其中的弱点。
- [RC4](https://ssl.sh/zh/glossary/rc4/): RC4 是 Ron Rivest 在 1987 年设计的流密码，曾在 SSL/TLS 中广泛使用，因密钥流存在统计偏差，2015 年被 RFC 7465 禁止用于 TLS。