diff -up rsyslog-8.1911.0/grammar/rainerscript.c.orig rsyslog-8.1911.0/grammar/rainerscript.c
--- rsyslog-8.1911.0/grammar/rainerscript.c.orig	2021-04-06 13:43:55.366523373 +0200
+++ rsyslog-8.1911.0/grammar/rainerscript.c	2021-04-06 13:44:40.039239056 +0200
@@ -905,15 +905,29 @@ static int
 doGetGID(struct nvlst *valnode, struct cnfparamdescr *param,
 	  struct cnfparamvals *val)
 {
-	char *cstr;
-	int r;
-	struct group *resultBuf;
-	struct group wrkBuf;
-	char stringBuf[2048]; /* 2048 has been proven to be large enough */
+        char *cstr;
+        int r;
+        struct group *resultBuf = NULL;
+        struct group wrkBuf;
+        char *stringBuf = NULL;
+        size_t bufSize = 1024;
+        int e;
+
+        cstr = es_str2cstr(valnode->val.d.estr, NULL);
+        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));
 
-	cstr = es_str2cstr(valnode->val.d.estr, NULL);
-	const int e = getgrnam_r(cstr, &wrkBuf, stringBuf,
-		sizeof(stringBuf), &resultBuf);
 	if(resultBuf == NULL) {
 		if(e != 0) {
 			LogError(e, RS_RET_ERR, "parameter '%s': error to "
@@ -929,6 +943,7 @@ doGetGID(struct nvlst *valnode, struct c
 		   param->name, (int) resultBuf->gr_gid, cstr);
 		r = 1;
 	}
+	free(stringBuf);
 	free(cstr);
 	return r;
 }