CVE-2026-40685

6.5 MEDIUM 0.3% exploit odds Fix listed Memory safety Server

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of service disruption.
Exploit odds: 0.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-04-30 22:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 10:45 UTC Last updatedMost recent change to the record

Details

Published: 2026-04-30 22:16 UTC
Last modified: 2026-06-17 10:45 UTC
Exploit probability: 0.3% · EPSS, next 30 days
Weakness: CWE-684
Record status: Analyzed

Affected

Exim < 4.99.2

Attack profile CVSS 3.1 · 6.5

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: High

Raw vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

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Fix and advisories

References

NVD record · CVE.org record