Exim before 4.99.3, in certain GnuTLS configurations, has a remotely reachable use-after-free in the BDAT body parsing path. It is triggered when a client sends a TLS close_notify mid-body during a CHUNKING transfer, followed by a final cleartext byte on the same TCP connection. This can lead to heap corruption. An unauthenticated network attacker exploiting this vulnerability could execute arbitrary code.
PoC: POC_CVE-2026-45185
POC_CVE-2026-45185 for nuclei-templates
PoC: cve-2026-45185-detection-script
These detection scripts are property of the SECPlayground Platform. Two safe detection scripts. Neither drives the close_notify-mid-BDAT trigger, so they will not crash the daemon or leave panic-log entries. Both verdicts are "likely vulnerable" — distinguishing GnuTLS from OpenSSL builds remotely is not reliable without exploitation.
PoC: Dead.Letter-CVE-2026-45185
Dead.Letter CVE-2026-45185 EXIM Vulnerability Detection Script
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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