Cyber Resilience

CVE-2026-40686

Low

Published: 30 April 2026

Published
30 April 2026
Modified
01 May 2026
KEV Added
—
Patch
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CVSS Score v3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS Score 0.0011 28.6th percentile
Risk Priority 7 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-40686 is a low-severity Out-of-bounds Read (CWE-125) vulnerability in Exim Exim. Its CVSS base score is 3.7 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 28.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail…

more

message.

CWE(s)
CWE-125

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Why these techniques?

Out-of-bounds read in public-facing Exim mail server enables exploitation for information disclosure via malformed email headers.

Confidence: MEDIUM · MITRE ATT&CK Enterprise v18.1

Affected Assets

exim
exim
≤ 4.99.2

Mitigating Controls

No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.

References