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01 Record

CVE-2026-46428

lettre has TLS hostname verification disabled when using Boring TLS backend

CriticalPUBLISHEDCNA: GitHub_M
CNA base score9.1 CVSS v4.0CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N
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02 Description

lettre has TLS hostname verification disabled when using Boring TLS backend

03 Exploitation and scoring

Exploitation
Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.
SSVC decision
  • ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
  • AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
  • Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.31% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 24.6% of scored records. A rank, not a probability.
NVD base score
9.1 (CVSS v4.0), scored by the NVD independently of the CNA.
NVD CVSS vector
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
NVD analysis status
Deferred. NVD last modified this record on 2026-07-23.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-07-20 15:37Z3 MO AGO
Last updated
2026-07-21 15:49Z3 MO AGO
Reserved
2026-05-13
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
Critical (CVSS 9.1)
CNA CVSS vector
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
Weaknesses
  • CWE-295Improper Certificate ValidationBase
Data version
5.2
Document digest
0446833dbacf15199bb530a25234eeb7971e2a89ea7a8d3774e02ec16c6516a7

05 Affected products

VendorProductVersionsPlatforms
lettrelettre>= 0.10.1, < 0.11.22—

06 References