CVE-2026-40687

Description

In Exim before 4.99.2, when the SPA authentication driver is used with an adversarial SPA resource, there can be an out-of-bounds write that crashes the connection instance, or erroneous data processing that divulges data from uninitialized heap memory.

CVSS v3.1 Score

4.8

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L

EPSS — Exploit Prediction

0.0017

Probability of exploitation

0.37%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-909 CWE-909

Affected Products

Vendor	Product	Versions
exim	exim	< 4.99.2

References

Advisories & Patches

https://code.exim.org/exim/exim/commit/68b963b9f75ca27b38e1c0f8c87037990199f505 https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40687.assessment

Other References

https://exim.org/static/doc/security/CVE-2026-40687.txt https://www.openwall.com/lists/oss-security/2026/04/30/21

Frequently Asked Questions

What is CVE-2026-40687? +

In Exim before 4.99.2, when the SPA authentication driver is used with an adversarial SPA resource, there can be an out-of-bounds write that crashes the connection instance, or erroneous data processing that divulges data from uninitialized heap memory. It has a CVSS v3.1 base score of 4.8 (MEDIUM).

How severe is CVE-2026-40687? +

CVE-2026-40687 has a CVSS v3.1 score of 4.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0017, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-40687? +

CVE-2026-40687 affects products from exim, specifically: exim. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-40687? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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