Critical severity · published Apr 30, 2026
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…
9.1
CVSS
0.4%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 31% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
EX
Exim · Exim
before 4.99.2 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40687
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-40687
Patch
https://code.exim.org/exim/exim/commit/68b963b9f75ca27b38e1c0f8c87037990199f505
Broken Link
https://exim.org/static/doc/security/CVE-2026-40687.txt
Vendor Advisory
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40687.assessment
Mailing List
https://www.openwall.com/lists/oss-security/2026/04/30/21
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