SEPTEMBER 7, 2026
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Case File

CVE-2026-46428

CRITICAL · CVSS 9.1 EPSS 0.19% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-07-20 · Last synced 2026-08-19

CyberRota Analysis

AI-Generated

The lettre mailer library for Rust, specifically versions 0.10.1 to 0.11.22, contains an inverted-boolean bug in its `boring-tls` integration that disables TLS hostname verification, allowing on-path attackers to intercept SMTP submissions and access sensitive credentials and message contents. Users of lettre utilizing the `boring-tls` feature should prioritize upgrading to version 0.11.22 to mitigate this vulnerability, as it poses a significant risk to the confidentiality of email communications.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-46428
Severity
CRITICAL
CVSS
9.1
EPSS
0.19%

Original NVD Description

lettre is a a mailer library for Rust. Starting in version 0.10.1 and prior to version 0.11.22, an inverted-boolean bug in lettre's `boring-tls` integration silently disables TLS hostname verification for callers using the default (strict) configuration. An on-path attacker presenting any chain-valid certificate for any domain can intercept SMTP submission, including PLAIN/LOGIN credentials and message contents, against any lettre user built with the `boring-tls` feature. Other TLS backends (`native-tls`, `rustls`) are unaffected. Version 0.11.22 patches the issue.