CVE-2026-40687
Exim SPA Authentication Driver Uninitialized Memory Disclosure
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.
INFO
Published Date :
April 30, 2026, 10:16 p.m.
Last Modified :
May 1, 2026, 7:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 8254265b-2729-46b6-b9e3-3dfca2d5bfca | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE | ||||
| CVSS 3.1 | CRITICAL | [email protected] |
Solution
- Update Exim to version 4.99.2 or later.
- Review SPA authentication driver configuration.
- Implement input validation for SPA resources.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40687.
| URL | Resource |
|---|---|
| https://code.exim.org/exim/exim/commit/68b963b9f75ca27b38e1c0f8c87037990199f505 | Patch |
| https://exim.org/static/doc/security/CVE-2026-40687.txt | Broken Link |
| https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40687.assessment | Vendor Advisory |
| https://www.openwall.com/lists/oss-security/2026/04/30/21 | Mailing List Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40687 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40687
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40687 vulnerability anywhere in the article.
-
CybersecurityNews
Multiple Exim Mail Server Vulnerabilities Leads to Crash with Malicious DNS data
The Exim development team has released version 4.99.2 to address four newly discovered security vulnerabilities affecting their mail server software. These flaws allow attackers to potentially crash s ... Read more
The following table lists the changes that have been made to the
CVE-2026-40687 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
May. 01, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:* versions up to (excluding) 4.99.2 Added Reference Type MITRE: https://code.exim.org/exim/exim/commit/68b963b9f75ca27b38e1c0f8c87037990199f505 Types: Patch Added Reference Type MITRE: https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40687.assessment Types: Vendor Advisory Added Reference Type MITRE: https://exim.org/static/doc/security/CVE-2026-40687.txt Types: Broken Link Added Reference Type MITRE: https://www.openwall.com/lists/oss-security/2026/04/30/21 Types: Mailing List, Third Party Advisory -
CVE Modified by [email protected]
May. 01, 2026
Action Type Old Value New Value Added Reference https://exim.org/static/doc/security/CVE-2026-40687.txt Removed Reference https://exim.org/static/doc/security/CVE-2025-40687.txt -
New CVE Received by [email protected]
Apr. 30, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L Added CWE CWE-909 Added Reference https://code.exim.org/exim/exim/commit/68b963b9f75ca27b38e1c0f8c87037990199f505 Added Reference https://exim.org/static/doc/security/CVE-2025-40687.txt Added Reference https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40687.assessment Added Reference https://www.openwall.com/lists/oss-security/2026/04/30/21