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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.37%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 3.1
- 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- EPSS
- 0.37% probability · 31th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-909
- Affected
- exim/exim
- Source
- cve@mitre.org
References
- https://code.exim.org/exim/exim/commit/68b963b9f75ca27b38e1c0f8c87037990199f505Patch
- https://exim.org/static/doc/security/CVE-2026-40687.txtBroken Link
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40687.assessmentVendor Advisory
- https://www.openwall.com/lists/oss-security/2026/04/30/21Mailing List, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.