Vulnerability · Published Apr 30, 2026 · Assigned by mitre
CVE-2026-40686
Low 3.7
In plain English
A low-severity out-of-bounds read in Exim from Exim. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 16% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)3.7Low
Exploit odds (30 days)0.2%top 84.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | exim | 4.98.2-r0 | ALPINE-CVE-2026-40686 |
| Alpine:v3.24 | exim | 4.98.2-r0 | ALPINE-CVE-2026-40686 |
| Debian:12 | exim4 | 4.96-15+deb12u9 | DEBIAN-CVE-2026-40686 |
| Debian:13 | exim4 | 4.98.2-1+deb13u2 | DEBIAN-CVE-2026-40686 |
| Debian:14 | exim4 | 4.99.2-1 | DEBIAN-CVE-2026-40686 |
| Ubuntu:22.04:LTS | exim4 | 4.95-4ubuntu2.7 | UBUNTU-CVE-2026-40686 |
| Ubuntu:24.04:LTS | exim4 | 4.97-4ubuntu4.4 | UBUNTU-CVE-2026-40686 |
| Ubuntu:25.10 | exim4 | 4.98.2-1ubuntu2.1 | UBUNTU-CVE-2026-40686 |
| Ubuntu:26.04:LTS | exim4 | 4.99.1-1ubuntu1.1 | UBUNTU-CVE-2026-40686 |
Affected products (as reported)
Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N