PT-2026-36197 · Exim+3 · Exim+3

Bernard Quatermass · CVE-2026-40686 · Published 2026-03-23 · Updated 2026-07-29

Positive Technologies (AI Summary)

CVSS v3.1

5.3

Medium

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Name of the Vulnerable Software and Affected Versions Exim versions prior to 4.99.2

Description An out-of-bounds read occurs when utf8 operators are enabled and malformed UTF-8 header data containing large UTF-8 trailing characters is processed. This issue may allow a remote attacker to cause sensitive information to be disclosed within an error message generated during the handling of an unrelated e-mail message.

Recommendations Update to version 4.99.2 or later. As a temporary workaround, disable utf8 operators to minimize the risk of exploitation.

Fix

DoS

Out of bounds Read

Weakness Enumeration

CWE-125

Related Identifiers

BDU:2026-09404

CVE-2026-40686

USN-8228-1

USN-8382-1

Affected Products

Exim

Linuxmint

Red Os

Ubuntu

References · 33

• https://osv.dev/vulnerability/USN-8228-1 · Vendor Advisory
• https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-40686 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-40686 · Vendor Advisory
• https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc · Patch
• https://osv.dev/vulnerability/USN-8382-1 · Vendor Advisory
• https://ubuntu.com/security/notices/USN-8228-1 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-40687 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2026-40686 · Security Note
• https://ubuntu.com/security/CVE-2026-48840 · Vendor Advisory
• https://wiki.astralinux.ru/astra-linux-se18-bulletin-2026-0611SE18HF · Vendor Advisory
• https://bdu.fstec.ru/vul/2026-09404 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2026-40686 · Security Note
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-40686 · Vendor Advisory
• https://ubuntu.com/security/notices/USN-8382-1 · Vendor Advisory