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Graph/aa548851-9410-4650-bdfc-eeed791ec080

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Shell Scripting

aa548851-9410-4650-bdfc-eeed791ec080

Shell Scripting

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Updated5/1/2026

PageRank0.0001

Effectiveness0.000

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17 linked nodes

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SUPPORTSComponent

PERTAIN_TOReport

Bash cutover verification scripts exited early under set -e despite successful checks

PERTAIN_TOReport

pkill -f with a pattern that appears in your own command line kills the invoking shell (exit 144 / SIGTERM)

PERTAIN_TOProblem

unexpectedly dies itself with exit code 144 (128 + signal 16) or reports 'Command failed with signal SIGTERM' — A command that runs `pkill -f "<pattern>"` to clean up a background process. Tension: the intended relaunch/cleanup never completes. Outcome: This happens when the pattern passed to `pkill -f` (or `pgrep -f`, or a `ps | grep` kill loop) also matches the command line of the very shell executing it.

PERTAIN_TOSolution

Don't pkill by a pattern that can match your own command. — `pkill -f`/`pgrep -f` see the full command line of the calling shell. Tension: any self-referential pattern is a self-kill.

PERTAIN_TOReport

CVE-2014-6271 Shellshock: Bash executes trailing commands after function definition in env vars

PERTAIN_TOReport

CVE-2014-6271 (Shellshock): Environment Variable Function Definition Injection in bash-4.3

PERTAIN_TOReport

CVE-2014-6271 Shellshock: bash parse_and_execute consumes trailing commands after function-definition env import

PERTAIN_TOReport

CVE-2014-6271 Shellshock: Bash executes trailing commands after function definition imported from env vars

PERTAIN_TOSolution

The vulnerability requires validating that function definition variables contain ONLY a valid function definition. — Bash 4.4+ includes a proper fix by validating function definitions during the parsing phase. Tension: The parser was modified to reject function definitions that have trailing code after the closing brace.

PERTAIN_TORootCause

Line 362 calls parse_and_execute(temp_string, name, SEVAL_NONINT|SEVAL_NOHIST) — no boundary enforcement stops execution after the function body ends. Tension: The parser executes ALL commands in the string — including anything after the closing brace of the function body. Outcome: no boundary enforcement stops execution after the function body ends.

PERTAIN_TOProblem

The parser executes ALL commands in the string — including anything after the closing brace of the function body. — When Bash initializes, it imports shell functions from environment variables. Outcome: This allows arbitrary command execution.

PERTAIN_TOProblem

bash initializes, initialize_shell_variables() in variables.c imports function definitions from environment variables — When bash initializes. Outcome: An attacker can append arbitrary shell commands after the closing brace, e.g., VAR='() { :;}; /usr/bin/id', and they will be executed.

PERTAIN_TORootCause

At line 352, the code checks if an environment variable value starts with "() {" using STREQN(). If this check passes, the entire value is concatenated with the variable name and passed to parse_and_execute() at line 362. — in variables.c. Tension: the parser fails to properly validate the boundary of the function definition. Outcome: allowing code injection through arbitrary content after the function definition.

PERTAIN_TORootCause

execute_cmd.c:5785-5788. Tension: The forked subshell that interprets the script therefore runs WITHOUT rbash restrictions. Outcome: The behavior is even documented in repo file RBASH lines 34-36.

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