CVE-2026-40685: exim
CVSS: 9.8v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-40685DEBIAN-CVE-2026-40685CGA-2g6p-xqv4-6rwxCGA-4jpx-chfw-3vqcCGA-6cpq-jvmp-fp58CGA-f3h9-7c59-hhwqCGA-g74q-f2vm-gxf7CGA-g9qg-jxvw-6388CGA-gfcm-vv36-q65qCGA-gv75-fq8h-vr8gCGA-j3jr-4963-gxvxCGA-j7m5-4gwc-4884CGA-j7p8-5c5m-hr3fCGA-jf42-wwhv-6xv5CGA-jgwh-ppxh-fvfjCGA-jwph-3v95-m5mmCGA-m7h4-743h-87fxCGA-pqc6-xvcw-q58hCGA-qxw8-7gxx-gr4jCGA-r74c-vv4p-4g3jCGA-rv6j-66q9-j6rrCGA-wr8j-phw4-rjf7
Published 30-04-2026Last modified 01-05-2026
Vulnerability summary
CVE-2026-40685 is a critical (CVSS 9.8) vulnerability in exim. EPSS estimates a 0.57% chance of exploitation in the next 30 days, higher than 46.3% of scored vulnerabilities.
CVSS score
9.8/10
010
Critical · v3.1 (NVD)EPSS score
0.57%
0%100%
Low · +0.25 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 1 · Related 3Timeline
- 30-04-2026PublishedVulnerability first disclosed.
- 01-05-2026Last modifiedVulnerability information updated.
Description
In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encounters malformed JSON in an untrusted header, because of an incorrect implementation of \ skipping.
CVSS metrics
4 scores · 4 sources · 1 versionCritical 9.8Preferred score · NVD (NIST)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HSources4 sources · 6.5–9.8
- CVE.orgCNA6.5MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:HDiffers
- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.57%
Chance of exploitation in the next 30 days
Percentile
46%
Versus all other CVEs
30-day change
+0.25 pp
From 0.32% on 19-09-2026
19-09-202619-10-2026
EPSS score0.57%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Chainguard10 products
- exim< 4.99.5-r0
- exim-cdb< 4.99.5-r0
- exim-dbmdb< 4.99.5-r0
- exim-dnsdb< 4.99.5-r0
- exim-doc< 4.99.5-r0
Wolfi10 products
- exim< 4.99.5-r0
- exim-cdb< 4.99.5-r0
- exim-dbmdb< 4.99.5-r0
- exim-dnsdb< 4.99.5-r0
- exim-doc< 4.99.5-r0
Debian1 product
- exim4< 4.96-15+deb12u9 | < 4.98.2-1+deb13u2 | < 4.99.2-1
Exim1 product
- exim< 4.99.2
Ubuntu1 product
- exim4All versions (No fix recorded) | < 4.93-13ubuntu1.12+esm1 | < 4.95-4ubuntu2.7 | < 4.97-4ubuntu4.4 | < 4.98.2-1ubuntu2.1 | < 4.99.1-1ubuntu1.1
5 vendors · 23 products
