New Exim BDAT Vulnerability Exposes GnuTLS Builds to Potential Code Execution

What’s new: Exim has released security updates to address a severe use-after-free vulnerability, tracked as CVE-2026-45185 (Dead.Letter), affecting GnuTLS builds. This vulnerability can lead to memory corruption and potential code execution during BDAT message body handling when a TLS connection is established. The issue affects Exim versions from 4.97 to 4.99.2 that use GnuTLS.

Who’s affected

All Exim installations using GnuTLS (USE_GNUTLS=yes) from versions 4.97 to 4.99.2 are impacted. Builds using other TLS libraries, such as OpenSSL, are not affected.

What to do

• Upgrade to Exim version 4.99.3 or later as soon as possible to mitigate the vulnerability.

Sources

• The Hacker News