MEDIUM
CVE-2026-40686
CWE-125Published: April 30, 2026· Updated: May 1, 2026
5.3
CVSS v3.1
EPSS:0.03%probability of exploitation in 30 daysPercentile:8.7th
Official Description
In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message.
Technical Analysis
CVE-2026-40686 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.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityLow
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
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
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Official Patches & Advisories
All References (4)
→
https://www.openwall.com/lists/oss-security/2026/04/30/21Mailing List · Third Party Advisory
Quick Facts
CVE IDCVE-2026-40686
CVSS Score5.3 / 10
SeverityMEDIUM
WeaknessCWE-125
CISA KEVNo
EPSS (30d)0.03%
Affected1 vendor
PublishedApr 30, 2026
Related CVEs (CWE-125)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-40686 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.