# CVE-2026-40685

> Vulnerability · severity: **MEDIUM** (CVSS 6.5).

## 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.

## Key facts

- **CVE ID:** CVE-2026-40685
- **Published:** 2026-04-30
- **CVSS severity:** MEDIUM
- **CVSS base score:** 6.5
- **CWE codes:** CWE-684, CWE-787

## Affected products

- `exim:exim`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40685

## Citation

> AI Analytics. CVE-2026-40685. Retrieved 2026-07-15 from https://api.ai-analytics.org/cve/CVE-2026-40685. Derived from NIST NVD. Licensed CC0.

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