HOMEVULNERABILITIESCVE-2026-40687
CRITICAL

CVE-2026-40687

CWE-909Published: April 30, 2026· Updated: May 1, 2026

9.1
CVSS v3.1
EPSS:0.07%probability of exploitation in 30 daysPercentile:19.8th

Official 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.

NVD Source

Technical Analysis

CVE-2026-40687 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), availability disruption (denial of service), with a CVSS base score of 9.1.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected Vendors & Products

exim1 product
exim
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://code.exim.org/exim/exim/commit/68b963b9f75ca27b38e1c0f8c87037990199f505
ADVISORYhttps://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40687.assessment
ADVISORYhttps://www.openwall.com/lists/oss-security/2026/04/30/21

All References (4)

→
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

Quick Facts

CVE IDCVE-2026-40687
CVSS Score9.1 / 10
SeverityCRITICAL
WeaknessCWE-909
CISA KEVNo
EPSS (30d)0.07%
Affected1 vendor
PublishedApr 30, 2026

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2026-40687 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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