Bug 2502719 (CVE-2026-16461)

A flaw was found in rpcbind's rpcinfo utility. In rpcbdump() short mode, used by `rpcinfo -s`, version values returned by a remote RPCBPROC_DUMP reply are appended via unbounded sprintf() calls into a fixed 256-byte stack buffer without tracking remaining space:

```c
char buf[256];
char *p = buf;
for (vl = rs->vlist; vl; vl = vl->next) {
    sprintf (p, "%d", vl->vers);
    p = p + strlen (p);
    if (vl->next)
        sprintf (p++, ",");
}
```

A malicious or compromised rpcbind endpoint that returns enough distinct version numbers for a single program (roughly 24 maximum-width decimal values plus separators) can overflow this buffer. A user or administrator must run `rpcinfo -s <host>` against the hostile endpoint; no privileges on the victim are required, but user interaction is needed. Current evidence supports client-side stack memory corruption leading to a crash/denial of service of the `rpcinfo` client process; disclosure or reliable code execution are not established.

This bug was originally reported bundled together with a related, since-fixed overflow in rpcbaddrlist() (now tracked separately as CVE-2026-16277). Confirmed via direct inspection of upstream commit bb9bb7286a4c345442946dc2ce3c9e7f67e96d4d (rpcbind 1.2.9) that this rpcbdump() short-mode overflow is NOT fixed by that commit and remains present in the latest upstream release.

Steps to reproduce:
1. Build rpcbind with AddressSanitizer: `CFLAGS="-O1 -g -fsanitize=address -fno-omit-frame-pointer" ./configure && make -j`
2. Run a malicious rpcbind-compatible endpoint, or an instrumented test responder.
3. Return an RPCBPROC_DUMP list for one program with enough distinct versions (~24+ max-width decimal values) to exceed 256 bytes.
4. Run `./src/rpcinfo -s <attacker-host>`.
5. Observe an ASan stack-buffer-overflow report or client crash.

Proposed fix (not yet applied upstream): convert the version-list formatter to bounded snprintf() calls that track remaining buffer space.
```diff
 char *p = buf;
+char *p = buf;
+size_t rem = sizeof(buf);
+int n;
+buf[0] = '\0';
 for (vl = rs->vlist; vl; vl = vl->next) {
-  sprintf (p, "%d", vl->vers);
-  p = p + strlen (p);
-  if (vl->next)
-    sprintf (p++, ",");
+  n = snprintf(p, rem, "%d%s", vl->vers, vl->next ? "," : "");
+  if (n < 0)
+    break;
+  if ((size_t)n >= rem) {
+    p = buf + sizeof(buf) - 1;
+    break;
+  }
+  p += n;
+  rem -= (size_t)n;
 }
```