Exim BDAT Use-After-Free 'Dead.Letter' Patch Released
🔒 Exim has issued emergency updates to fix CVE-2026-45185, dubbed Dead.Letter, a critical use-after-free in BDAT message body parsing that manifests when TLS is handled via GnuTLS. The flaw is triggered when a client sends a TLS close_notify during an active BDAT transfer and then follows up with a final cleartext byte on the same TCP connection, which can corrupt heap metadata and enable code execution. It affects Exim 4.97 through 4.99.2 built with USE_GNUTLS=yes and is fixed in 4.99.3; there are no mitigations, so administrators should apply the update immediately.
