New Exim BDAT GnuTLS Vulnerability Enables Code Execution Attacks

**Exim BDAT GnuTLS vulnerability (EXIM-Security-2026-05-01.1):** A use-after-free in Exim's GnuTLS backend can be triggered when a TLS close_notify is sent mid-BDAT transfer and one additional plaintext byte is sent, enabling heap corruption and potential remote code execution on Exim builds compiled with USE_GNUTLS=yes (affecting 4.97–4.99.2); Exim released 4.99.3 on May 12, 2026 to fix the issue and administrators are urged to upgrade immediately as no mitigation other than patching is available.