CVE-2026-46428

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 75% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
57(Track*)
EG Risk 57/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
25%
KEV
Not listed

Published

July 20, 2026

Last Modified

July 23, 2026

Advisory Details (4)

Auto-updated Sep 7, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github.
github Patch Available🟡 PoC Available

TLS hostname verification disabled when using Boring TLS backend · Advisory · lettre/lettre · GitHub

https://github.com/lettre/lettre/security/advisories/GHSA-4pj9-g833-qx53
generic

RUSTSEC-2026-0141: lettre: TLS hostname verification disabled when using Boring TLS backend › RustSec Advisory Database

https://rustsec.org/advisories/RUSTSEC-2026-0141.html
github_release Patch Available

v0.11.22 - update now if you're using Boring TLS

Patch available: lettre/lettre v0.11.22

https://github.com/lettre/lettre/releases/tag/v0.11.22
github_commit Patch Available

commit f5efffc88360 (lettre/lettre)

Patch available: lettre/lettre v0.11.22 (contains commit f5efffc88360)

https://github.com/lettre/lettre/commit/f5efffc88360dbdbfcef80f465e42d5bce68ca35

Vendor Advisories for CVE-2026-46428(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
crates.io(1)
PackageVulnerable rangeFixed inDependents
lettre—0.11.22—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 47× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-11 18:32 UTCEG score recompute
  2. 2026-09-11 14:53 UTCEPSS rescore
  3. 2026-09-11 09:37 UTCEPSS rescore
  4. 2026-09-11 09:28 UTCEG score recompute
  5. 2026-09-10 09:34 UTCEPSS rescore
  6. 2026-09-09 11:56 UTCEG score recompute
  7. 2026-09-08 22:00 UTCEPSS rescore
  8. 2026-09-07 22:55 UTCEG score recompute
  9. 2026-09-07 16:01 UTCEPSS rescore
  10. 2026-09-06 16:55 UTCEG score recompute
  11. 2026-09-06 13:47 UTCEPSS rescore
  12. 2026-09-05 19:52 UTCEG score recompute
  13. 2026-09-05 09:33 UTCEG score recompute
  14. 2026-09-04 05:06 UTCEPSS rescore
  15. 2026-09-02 14:12 UTCEPSS rescore
  16. 2026-09-01 13:54 UTCEPSS rescore
  17. 2026-08-30 20:10 UTCEG score recompute
  18. 2026-08-30 19:17 UTCEPSS rescore
  19. 2026-08-30 02:37 UTCEG score recompute
  20. 2026-08-30 01:22 UTCEPSS rescore
  21. 2026-08-28 21:41 UTCEPSS rescore
  22. 2026-08-27 21:20 UTCEG score recompute
  23. 2026-08-27 14:25 UTCEPSS rescore
  24. 2026-08-26 22:09 UTCEG score recompute
  25. 2026-08-26 14:46 UTCEPSS rescore
Show 70 more
  1. 2026-08-25 18:44 UTCEG score recompute
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-24 18:58 UTCEG score recompute
  4. 2026-08-24 13:26 UTCEG score recompute
  5. 2026-08-23 01:51 UTCEG score recompute
  6. 2026-08-23 00:19 UTCEPSS rescore
  7. 2026-08-22 03:54 UTCEG score recompute
  8. 2026-08-21 23:49 UTCEPSS rescore
  9. 2026-08-21 01:36 UTCEG score recompute
  10. 2026-08-20 22:55 UTCEPSS rescore
  11. 2026-08-19 22:50 UTCEG score recompute
  12. 2026-08-19 17:04 UTCEPSS rescore
  13. 2026-08-18 19:36 UTCEG score recompute
  14. 2026-08-18 13:48 UTCEPSS rescore
  15. 2026-08-16 18:33 UTCEG score recompute
  16. 2026-08-16 14:56 UTCEPSS rescore
  17. 2026-08-16 05:24 UTCEG score recompute
  18. 2026-08-16 02:14 UTCEPSS rescore
  19. 2026-08-15 03:07 UTCEG score recompute
  20. 2026-08-15 01:30 UTCEPSS rescore
  21. 2026-08-14 00:51 UTCEG score recompute
  22. 2026-08-13 22:00 UTCEPSS rescore
  23. 2026-08-12 17:42 UTCEG score recompute
  24. 2026-08-12 13:51 UTCEPSS rescore
  25. 2026-08-11 15:22 UTCEG score recompute
  26. 2026-08-11 02:13 UTCEG score recompute
  27. 2026-08-11 00:00 UTCEPSS rescore
  28. 2026-08-09 15:12 UTCEG score recompute
  29. 2026-08-09 13:46 UTCEPSS rescore
  30. 2026-08-08 17:18 UTCEG score recompute
  31. 2026-08-08 16:37 UTCEPSS rescore
  32. 2026-08-07 19:25 UTCEG score recompute
  33. 2026-08-06 17:09 UTCEG score recompute
  34. 2026-08-06 13:47 UTCEPSS rescore
  35. 2026-08-05 23:38 UTCEG score recompute
  36. 2026-08-05 19:17 UTCEPSS rescore
  37. 2026-08-04 18:45 UTCEG score recompute
  38. 2026-08-04 15:10 UTCEPSS rescore
  39. 2026-08-04 14:22 UTCEG score recompute
  40. 2026-08-04 10:39 UTCEPSS rescore
  41. 2026-08-03 11:55 UTCEG score recompute
  42. 2026-08-03 10:36 UTCEPSS rescore
  43. 2026-08-02 04:24 UTCEG score recompute
  44. 2026-08-02 02:27 UTCEPSS rescore
  45. 2026-08-01 06:29 UTCEG score recompute
  46. 2026-08-01 04:16 UTCEPSS rescore
  47. 2026-07-30 18:57 UTCEG score recompute
  48. 2026-07-30 16:28 UTCEPSS rescore
  49. 2026-07-30 09:25 UTCEG score recompute
  50. 2026-07-30 05:01 UTCEG score recompute
  51. 2026-07-30 01:30 UTCEPSS rescore
  52. 2026-07-28 17:03 UTCEG score recompute
  53. 2026-07-28 15:36 UTCEPSS rescore
  54. 2026-07-27 17:37 UTCEG score recompute
  55. 2026-07-27 14:13 UTCEPSS rescore
  56. 2026-07-26 15:11 UTCEG score recompute
  57. 2026-07-26 14:54 UTCEPSS rescore
  58. 2026-07-26 14:54 UTCEPSS rescore
  59. 2026-07-26 10:48 UTCEG score recompute
  60. 2026-07-26 04:30 UTCEG score recompute
  61. 2026-07-25 14:18 UTCEPSS rescore
  62. 2026-07-24 14:17 UTCEPSS rescore
  63. 2026-07-23 14:18 UTCEPSS rescore
  64. 2026-07-23 03:17 UTCEG score recompute
  65. 2026-07-22 23:37 UTCEG score recompute
  66. 2026-07-22 14:08 UTCEPSS rescore
  67. 2026-07-21 15:24 UTCEPSS rescore
  68. 2026-07-20 16:37 UTCEG score recompute
  69. 2026-07-20 16:03 UTCEG score recompute
  70. 2026-07-20 16:02 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-46428?
CVE-2026-46428 is a critical vulnerability published on July 20, 2026. 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…
When was CVE-2026-46428 disclosed?
CVE-2026-46428 was first published in the National Vulnerability Database on July 20, 2026, with the most recent update on July 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-46428 actively exploited?
CVE-2026-46428 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 75.4% of all scored CVEs.
What is the CVSS score of CVE-2026-46428?
CVE-2026-46428 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-46428?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-46428, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-46428

Explore →

Is Your Infrastructure Affected by CVE-2026-46428?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs