CVE-2026-40686

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.

CVSS v3 3.7 LOW

3.7^/10

CVSS v3 : LOW

Vector :

Exploitability : 2.2 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc	Patch
https://exim.org/static/doc/security/CVE-2026-40686.txt	Broken Link
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment	Vendor Advisory
https://www.openwall.com/lists/oss-security/2026/04/30/21	Mailing List Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-04-30 22:16

Updated : 2026-06-17 10:45

NVD link : CVE-2026-40686

Mitre link : CVE-2026-40686

CVE.ORG link : CVE-2026-40686

JSON object : View

Products Affected

exim

exim

CWE

CWE-125

Out-of-bounds Read

{"id": "CVE-2026-40686", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-40686", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-05-01T14:27:01.351716Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "cve@mitre.org", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 3.7, "attackVector": "NETWORK", "baseSeverity": "LOW", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "LOW"}, "impactScore": 1.4, "exploitabilityScore": 2.2}, {"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.3, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "LOW"}, "impactScore": 1.4, "exploitabilityScore": 3.9}]}, "affected": [{"source": "cve@mitre.org", "affectedData": [{"vendor": "Exim", "product": "Exim", "versions": [{"status": "affected", "version": "0", "lessThan": "4.99.2", "versionType": "semver"}], "defaultStatus": "unaffected"}]}], "published": "2026-04-30T22:16:25.787", "references": [{"url": "https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc", "tags": ["Patch"], "source": "cve@mitre.org"}, {"url": "https://exim.org/static/doc/security/CVE-2026-40686.txt", "tags": ["Broken Link"], "source": "cve@mitre.org"}, {"url": "https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment", "tags": ["Vendor Advisory"], "source": "cve@mitre.org"}, {"url": "https://www.openwall.com/lists/oss-security/2026/04/30/21", "tags": ["Mailing List", "Third Party Advisory"], "source": "cve@mitre.org"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "cve@mitre.org", "description": [{"lang": "en", "value": "CWE-125"}]}], "descriptions": [{"lang": "en", "value": "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."}], "lastModified": "2026-06-17T10:45:34.447", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "E48EAA99-95DA-4695-BBEA-16D09AA0A508", "versionEndExcluding": "4.99.2"}], "operator": "OR"}]}], "sourceIdentifier": "cve@mitre.org"}