diff --git a/cache.h b/cache.h
index 4e283be24e1286..ecbd88adba6124 100644
--- a/cache.h
+++ b/cache.h
@@ -656,6 +656,7 @@ const char *make_relative_path(const char *abs, const char *base);
 int normalize_path_copy(char *dst, const char *src);
 int longest_ancestor_length(const char *path, const char *prefix_list);
 char *strip_path_suffix(const char *path, const char *suffix);
+int daemon_avoid_alias(const char *path);
 
 /* Read and unpack a sha1 file into memory, write memory to a sha1 file */
 extern int sha1_object_info(const unsigned char *, unsigned long *);
diff --git a/daemon.c b/daemon.c
index 1b5ada6648da66..ce4800621cece3 100644
--- a/daemon.c
+++ b/daemon.c
@@ -101,53 +101,6 @@ static void NORETURN daemon_die(const char *err, va_list params)
 	exit(1);
 }
 
-static int avoid_alias(char *p)
-{
-	int sl, ndot;
-
-	/*
-	 * This resurrects the belts and suspenders paranoia check by HPA
-	 * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
-	 * does not do getcwd() based path canonicalizations.
-	 *
-	 * sl becomes true immediately after seeing '/' and continues to
-	 * be true as long as dots continue after that without intervening
-	 * non-dot character.
-	 */
-	if (!p || (*p != '/' && *p != '~'))
-		return -1;
-	sl = 1; ndot = 0;
-	p++;
-
-	while (1) {
-		char ch = *p++;
-		if (sl) {
-			if (ch == '.')
-				ndot++;
-			else if (ch == '/') {
-				if (ndot < 3)
-					/* reject //, /./ and /../ */
-					return -1;
-				ndot = 0;
-			}
-			else if (ch == 0) {
-				if (0 < ndot && ndot < 3)
-					/* reject /.$ and /..$ */
-					return -1;
-				return 0;
-			}
-			else
-				sl = ndot = 0;
-		}
-		else if (ch == 0)
-			return 0;
-		else if (ch == '/') {
-			sl = 1;
-			ndot = 0;
-		}
-	}
-}
-
 static char *path_ok(char *directory)
 {
 	static char rpath[PATH_MAX];
@@ -157,7 +110,7 @@ static char *path_ok(char *directory)
 
 	dir = directory;
 
-	if (avoid_alias(dir)) {
+	if (daemon_avoid_alias(dir)) {
 		logerror("'%s': aliased", dir);
 		return NULL;
 	}
diff --git a/http-backend.c b/http-backend.c
index 646e9108bddbd5..f8ea9d7faa0494 100644
--- a/http-backend.c
+++ b/http-backend.c
@@ -559,7 +559,13 @@ static char* getdir(void)
 	if (root && *root) {
 		if (!pathinfo || !*pathinfo)
 			die("GIT_PROJECT_ROOT is set but PATH_INFO is not");
+		if (daemon_avoid_alias(pathinfo))
+			die("'%s': aliased", pathinfo);
 		strbuf_addstr(&buf, root);
+		if (buf.buf[buf.len - 1] != '/')
+			strbuf_addch(&buf, '/');
+		if (pathinfo[0] == '/')
+			pathinfo++;
 		strbuf_addstr(&buf, pathinfo);
 		return strbuf_detach(&buf, NULL);
 	} else if (path && *path) {
diff --git a/path.c b/path.c
index 047fdb0a1fe815..c7679be5c8727c 100644
--- a/path.c
+++ b/path.c
@@ -564,3 +564,50 @@ char *strip_path_suffix(const char *path, const char *suffix)
 		return NULL;
 	return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 }
+
+int daemon_avoid_alias(const char *p)
+{
+	int sl, ndot;
+
+	/*
+	 * This resurrects the belts and suspenders paranoia check by HPA
+	 * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
+	 * does not do getcwd() based path canonicalizations.
+	 *
+	 * sl becomes true immediately after seeing '/' and continues to
+	 * be true as long as dots continue after that without intervening
+	 * non-dot character.
+	 */
+	if (!p || (*p != '/' && *p != '~'))
+		return -1;
+	sl = 1; ndot = 0;
+	p++;
+
+	while (1) {
+		char ch = *p++;
+		if (sl) {
+			if (ch == '.')
+				ndot++;
+			else if (ch == '/') {
+				if (ndot < 3)
+					/* reject //, /./ and /../ */
+					return -1;
+				ndot = 0;
+			}
+			else if (ch == 0) {
+				if (0 < ndot && ndot < 3)
+					/* reject /.$ and /..$ */
+					return -1;
+				return 0;
+			}
+			else
+				sl = ndot = 0;
+		}
+		else if (ch == 0)
+			return 0;
+		else if (ch == '/') {
+			sl = 1;
+			ndot = 0;
+		}
+	}
+}
diff --git a/t/t5560-http-backend.sh b/t/t5560-http-backend.sh
index 908ba079d27b82..ed034bc980ca66 100755
--- a/t/t5560-http-backend.sh
+++ b/t/t5560-http-backend.sh
@@ -146,6 +146,37 @@ test_expect_success 'http.receivepack false' '
 	POST git-receive-pack 0000 "403 Forbidden"
 '
 
+run_backend() {
+	REQUEST_METHOD=GET \
+	GIT_PROJECT_ROOT="$HTTPD_DOCUMENT_ROOT_PATH" \
+	PATH_INFO="$2" \
+	git http-backend >act.out 2>act.err
+}
+
+path_info() {
+	if test $1 = 0; then
+		run_backend "$2"
+	else
+		test_must_fail run_backend "$2" &&
+		echo "fatal: '$2': aliased" >exp.err &&
+		test_cmp exp.err act.err
+	fi
+}
+
+test_expect_success 'http-backend blocks bad PATH_INFO' '
+	config http.getanyfile true &&
+
+	run_backend 0 /repo.git/HEAD &&
+
+	run_backend 1 /repo.git/../HEAD &&
+	run_backend 1 /../etc/passwd &&
+	run_backend 1 ../etc/passwd &&
+	run_backend 1 /etc//passwd &&
+	run_backend 1 /etc/./passwd &&
+	run_backend 1 /etc/.../passwd &&
+	run_backend 1 //domain/data.txt
+'
+
 cat >exp <<EOF
 
 ###  refs/heads/master