An integer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base). In sasl_io_start_packet(), adding sizeof(uint32_t) to a crafted SASL packet length prefix of 0xFFFFFFFC causes unsigned wraparound to zero, bypassing the nsslapd-maxsasliosize limit and leading to a heap buffer overflow of up to approximately 2 megabytes of attacker-controlled data. After a successful SASL bind with integrity protection (SSF > 0), a remote attacker can cause a Denial of Service (DoS) or achieve Remote Code Execution (RCE). In FreeIPA and Red Hat Identity Management deployments, any domain user with a valid Kerberos ticket, enrolled host, or service account can trigger this vulnerability over the network. This flaw is independent of CVE-2025-14905, which patched schema.c only and did not modify sasl_io.c.
No complete workaround exists; nsslapd-maxsasliosize is bypassed by the integer overflow. Mitigations that reduce exposure: restrict SASL mechanisms (disable DIGEST-MD5 if not required; GSSAPI cannot be disabled in FreeIPA/IdM without breaking Kerberos authentication); firewall LDAP ports (389/636) to trusted networks; monitor for SASL-framed packets with length prefix 0xFFFFFFFC through 0xFFFFFFFF; enable audit logging (nsslapd-auditlog-logging-enabled: on); on RHEL 8, upgrading glibc reduces RCE exploitability but does not eliminate DoS.