diff -up mod_auth_openidc-2.4.10/src/mod_auth_openidc.c.orig mod_auth_openidc-2.4.10/src/mod_auth_openidc.c
--- mod_auth_openidc-2.4.10/src/mod_auth_openidc.c.orig	2021-11-05 11:55:03.000000000 +0100
+++ mod_auth_openidc-2.4.10/src/mod_auth_openidc.c	2024-04-15 17:53:49.601539683 +0200
@@ -2537,6 +2537,20 @@ static apr_byte_t oidc_validate_redirect
 		oidc_error(r, "%s: %s", *err_str, *err_desc);
 		return FALSE;
 	}
+	if (       (strstr(url, "/%09") != NULL) || (oidc_util_strcasestr(url, "/%2f") != NULL)
+			|| (strstr(url, "/\t") != NULL)
+			|| (strstr(url, "/%68") != NULL) || (oidc_util_strcasestr(url, "/http:") != NULL)
+			|| (oidc_util_strcasestr(url, "/https:") != NULL) || (oidc_util_strcasestr(url, "/javascript:") != NULL)
+			|| (strstr(url, "/〱") != NULL) || (strstr(url, "/〵") != NULL)
+			|| (strstr(url, "/ゝ") != NULL) || (strstr(url, "/ー") != NULL)
+			|| (strstr(url, "/〱") != NULL) || (strstr(url, "/ｰ") != NULL)
+			|| (strstr(url, "/<") != NULL) || (oidc_util_strcasestr(url, "%01javascript:") != NULL)
+			|| (strstr(url, "/%5c") != NULL) || (strstr(url, "/\\") != NULL)) {
+		*err_str = apr_pstrdup(r->pool, "Invalid URL");
+		*err_desc = apr_psprintf(r->pool, "URL value \"%s\" contains illegal character(s)", url);
+		oidc_error(r, "%s: %s", *err_str, *err_desc);
+		return FALSE;
+	}
 
 	return TRUE;
 }
diff -up mod_auth_openidc-2.4.10/src/mod_auth_openidc.h.orig mod_auth_openidc-2.4.10/src/mod_auth_openidc.h
--- mod_auth_openidc-2.4.10/src/mod_auth_openidc.h.orig	2021-11-09 10:00:40.000000000 +0100
+++ mod_auth_openidc-2.4.10/src/mod_auth_openidc.h	2024-04-15 17:53:49.601539683 +0200
@@ -819,6 +819,7 @@ char *oidc_util_http_query_encoded_url(r
 char *oidc_util_get_full_path(apr_pool_t *pool, const char *abs_or_rel_filename);
 apr_byte_t oidc_enabled(request_rec *r);
 char *oidc_util_http_form_encoded_data(request_rec *r, const apr_table_t *params);
+char* oidc_util_strcasestr(const char *s1, const char *s2);
 
 /* HTTP header constants */
 #define OIDC_HTTP_HDR_COOKIE                            "Cookie"
diff -up mod_auth_openidc-2.4.10/src/util.c.orig mod_auth_openidc-2.4.10/src/util.c
--- mod_auth_openidc-2.4.10/src/util.c.orig	2021-11-05 11:55:03.000000000 +0100
+++ mod_auth_openidc-2.4.10/src/util.c	2024-04-15 17:53:49.602539684 +0200
@@ -435,6 +435,24 @@ char* oidc_util_javascript_escape(apr_po
     return output;
 }
 
+char* oidc_util_strcasestr(const char *s1, const char *s2) {
+	const char *s = s1;
+	const char *p = s2;
+	do {
+		if (!*p)
+			return (char*) s1;
+		if ((*p == *s) || (tolower(*p) == tolower(*s))) {
+			++p;
+			++s;
+		} else {
+			p = s2;
+			if (!*s)
+				return NULL;
+			s = ++s1;
+		}
+	} while (1);
+	return *p ? NULL : (char*) s1;
+}
 
 /*
  * get the URL scheme that is currently being accessed