diff -up rsyslog-8.24.0/grammar/rainerscript.c.doGetGID_overflow rsyslog-8.24.0/grammar/rainerscript.c
--- rsyslog-8.24.0/grammar/rainerscript.c.doGetGID_overflow	2021-03-30 15:56:51.605271073 +0200
+++ rsyslog-8.24.0/grammar/rainerscript.c	2021-03-30 15:59:57.758153756 +0200
@@ -832,12 +832,27 @@ doGetGID(struct nvlst *valnode, struct c
 {
 	char *cstr;
 	int r;
-	struct group *resultBuf;
+	struct group *resultBuf = NULL;
 	struct group wrkBuf;
-	char stringBuf[2048]; /* 2048 has been proven to be large enough */
+	char *stringBuf = NULL;
+	size_t bufSize = 1024;
+	int e;
 
 	cstr = es_str2cstr(valnode->val.d.estr, NULL);
-	getgrnam_r(cstr, &wrkBuf, stringBuf, sizeof(stringBuf), &resultBuf);
+	do {
+		char *p;
+
+		/* Increase bufsize and try again.*/
+		bufSize *= 2;
+		p = realloc(stringBuf, bufSize);
+		if(!p) {
+			e = ENOMEM;
+			break;
+		}
+		stringBuf = p;
+		e = getgrnam_r(cstr, &wrkBuf, stringBuf, bufSize, &resultBuf);
+	} while(!resultBuf && (e == ERANGE));
+
 	if(resultBuf == NULL) {
 		parser_errmsg("parameter '%s': ID for group %s could not "
 		  "be found", param->name, cstr);
@@ -849,6 +864,7 @@ doGetGID(struct nvlst *valnode, struct c
 		   param->name, (int) resultBuf->gr_gid, cstr);
 		r = 1;
 	}
+	free(stringBuf);
 	free(cstr);
 	return r;
 }