Command Injection Bypasses

Command injection filters typically block spaces, slashes, and known command names. Each bypass technique targets a specific filter type. Start with the simplest and move to more complex only if the simpler ones fail. Always confirm baseline injection works first — if whoami executes cleanly, only apply bypasses when a filtered character or keyword blocks further progress.

Space Bypass

Most filters check for literal space (0x20) but miss alternative whitespace and shell expansion:

Slash Bypass

When / is blocked, reconstruct the path from environment variables:

${PATH:0:1} extracts the first character from $PATH, which is always / on a standard Linux system.

Keyword Blacklist Bypass

Filters that match exact command strings miss these shell parsing tricks:

On Windows CMD, the caret ^ is an escape character and is ignored during execution:

Base64 Encoding

Encodes the entire command so no keywords or special characters appear in the request. The most reliable bypass for aggressive keyword filters:

Hex and Octal Encoding

Shell-level character encoding for when base64 itself is blocked:

Blind Injection Confirmation

When command output is not reflected in the response, confirm execution through timing or out-of-band callbacks: