CVE-2026-40684
Last modified
CVE-2026-40684 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. In Exim before 4.99.2, on systems using musl libc (not glibc), an attacker can crash the connection instance when malformed DNS data is present in PTR records. This is caused by a dn_expand oddity in octal printing.. EPSS estimates a 0.36% chance of exploitation in the next 30 days.
Description
In Exim before 4.99.2, on systems using musl libc (not glibc), an attacker can crash the connection instance when malformed DNS data is present in PTR records. This is caused by a dn_expand oddity in octal printing.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Exim | Exim | < 4.99.2 |
References
- https://www.openwall.com/lists/oss-security/2026/04/30/21Mailing List, Third Party Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2026-40684?
How severe is CVE-2026-40684?
How do I fix CVE-2026-40684?
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
Related CVEs from 2026
- CVE-2026-4066The Smart Custom Fields plugin for WordPress is vulnerable t…4.3
- CVE-2026-4067The Ad Short plugin for WordPress is vulnerable to Stored Cr…6.4
- CVE-2026-40677The use of insecure HTTP transport within AMD optional tools…7.7
- CVE-2026-4068The Add Custom Fields to Media plugin for WordPress is vulne…4.3
- CVE-2026-40682XML External Entity (XXE) via Unsanitized Dictionary Parsing…9.1
- CVE-2026-40683In OpenStack Keystone before 28.0.1, the LDAP identity backe…7.7
- CVE-2026-40685In Exim before 4.99.2, when JSON lookup is enabled, an out-o…9.8
- CVE-2026-40686In Exim before 4.99.2, when utf8 operators are enabled, ther…5.3
- CVE-2026-40687In Exim before 4.99.2, when the SPA authentication driver is…9.1
- CVE-2026-40688An out-of-bounds write vulnerability [CWE-787] vulnerability…7.2
- CVE-2026-4069The Alfie – Feed Plugin plugin for WordPress is vulnerable t…6.1
- CVE-2026-40690The asset dependency graph did not restrict nodes by the vie…4.3
Are you affected by CVE-2026-40684?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST