diff --git a/coregrind/m_gdbserver/remote-utils.c b/coregrind/m_gdbserver/remote-utils.c
index aa2cd4a..1b9ce76 100644
--- a/coregrind/m_gdbserver/remote-utils.c
+++ b/coregrind/m_gdbserver/remote-utils.c
@@ -323,10 +323,12 @@
    user = VG_(getenv)("LOGNAME");
    if (user == NULL) user = VG_(getenv)("USER");
    if (user == NULL) user = "???";
+   if (VG_(strchr)(user, '/')) user = "???";
 
    host = VG_(getenv)("HOST");
    if (host == NULL) host = VG_(getenv)("HOSTNAME");
    if (host == NULL) host = "???";
+   if (VG_(strchr)(host, '/')) host = "???";
 
    len = strlen(name) + strlen(user) + strlen(host) + 40;
 
diff --git a/coregrind/vgdb.c b/coregrind/vgdb.c
index d330cb5..160e6ee 100644
--- a/coregrind/vgdb.c
+++ b/coregrind/vgdb.c
@@ -517,10 +517,12 @@
    user = getenv("LOGNAME");
    if (user == NULL) user = getenv("USER");
    if (user == NULL) user = "???";
+   if (strchr(user, '/')) user = "???";
 
    host = getenv("HOST");
    if (host == NULL) host = getenv("HOSTNAME");
    if (host == NULL) host = "???";
+   if (strchr(host, '/')) host = "???";
 
    len = strlen(vgdb_prefix) + strlen(user) + strlen(host) + 40;
    from_gdb_to_pid = vmalloc (len);