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CVE-2026-40686

3.7 · LOW

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).

Published Apr 30, 2026CWE-125EPSS 0.40%

Overview

CVE-2026-40686 is a low-severity vulnerability. It was published on April 30, 2026 and has a CVSS 3.1 base score of 3.7 (LOW).

This vulnerability has a CVSS 3.1 base score of 3.7, rated LOW. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

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 message.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refcode.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efcRefexim.org/static/doc/security/CVE-2026-40686.txtRefexim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessmentRefwww.openwall.com/lists/oss-security/2026/04/30/21

How CyberStrike helps

Frequently asked questions

What is CVE-2026-40686?

CVE-2026-40686 is a low-severity vulnerability. It was published on April 30, 2026 and has a CVSS 3.1 base score of 3.7 (LOW).

How severe is CVE-2026-40686?

This vulnerability has a CVSS 3.1 base score of 3.7, rated LOW. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-40686?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-40686?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-40686 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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