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CVE

CVE-2026-46428

lettre has TLS hostname verification disabled when using Boring TLS backend
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CVE

CVE-2026-46428

lettre has TLS hostname verification disabled when using Boring TLS backend

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.

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
9.1
-
4.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
C
H
U
0
-
C
H
U
-

Related Resources

No items found.

References

https://github.com/lettre/lettre/releases/tag/v0.11.22, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46428.json, https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53, https://nvd.nist.gov/vuln/detail/CVE-2026-46428, https://rustsec.org/advisories/RUSTSEC-2026-0141.html, https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35

Severity

0

CVSS Score
0
10

Basic Information

Base CVSS
0
EPSS Probability
0.00319%
EPSS Percentile
0.24427%
Introduced Version
0c9fc6cb71650e49abc37540a48ffcbc2fe38ee4
Fix Available
9b88c4ff98fd8653cb389a66f885f02efd79ee6b

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