diff --git a/shell.c b/shell.c
index cef7ffdc9e..02cfd9627f 100644
--- a/shell.c
+++ b/shell.c
@@ -47,6 +47,8 @@ static void cd_to_homedir(void)
 		die("could not chdir to user's home directory");
 }
 
+#define MAX_INTERACTIVE_COMMAND (4*1024*1024)
+
 static void run_shell(void)
 {
 	int done = 0;
@@ -67,22 +69,46 @@ static void run_shell(void)
 	run_command_v_opt(help_argv, RUN_SILENT_EXEC_FAILURE);
 
 	do {
-		struct strbuf line = STRBUF_INIT;
 		const char *prog;
 		char *full_cmd;
 		char *rawargs;
+		size_t len;
 		char *split_args;
 		const char **argv;
 		int code;
 		int count;
 
 		fprintf(stderr, "git> ");
-		if (git_read_line_interactively(&line) == EOF) {
+
+		/*
+		 * Avoid using a strbuf or git_read_line_interactively() here.
+		 * We don't want to allocate arbitrary amounts of memory on
+		 * behalf of a possibly untrusted client, and we're subject to
+		 * OS limits on command length anyway.
+		 */
+		fflush(stdout);
+		rawargs = xmalloc(MAX_INTERACTIVE_COMMAND);
+		if (!fgets(rawargs, MAX_INTERACTIVE_COMMAND, stdin)) {
 			fprintf(stderr, "\n");
-			strbuf_release(&line);
+			free(rawargs);
 			break;
 		}
-		rawargs = strbuf_detach(&line, NULL);
+		len = strlen(rawargs);
+
+		/*
+		 * If we truncated due to our input buffer size, reject the
+		 * command. That's better than running bogus input, and
+		 * there's a good chance it's just malicious garbage anyway.
+		 */
+		if (len >= MAX_INTERACTIVE_COMMAND - 1)
+			die("invalid command format: input too long");
+
+		if (len > 0 && rawargs[len - 1] == '\n') {
+			if (--len > 0 && rawargs[len - 1] == '\r')
+				--len;
+			rawargs[len] = '\0';
+		}
+
 		split_args = xstrdup(rawargs);
 		count = split_cmdline(split_args, &argv);
 		if (count < 0) {
diff --git a/t/t9850-shell.sh b/t/t9850-shell.sh
index 2af476c3af..cfc71c3bd4 100755
--- a/t/t9850-shell.sh
+++ b/t/t9850-shell.sh
@@ -28,4 +28,10 @@ test_expect_success 'shell allows interactive command' '
 	test_cmp expect actual
 '
 
+test_expect_success 'shell complains of overlong commands' '
+	perl -e "print \"a\" x 2**12 for (0..2**19)" |
+	test_must_fail git shell 2>err &&
+	grep "too long" err
+'
+
 test_done