# CVE-2026-40685: exim4-daemon-heavy: In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encoun...

CVE-2026-40685 is fixed in 6 products on 1 platform, first by exim4 4.99.1-1ubuntu1.1, released April 29, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-40685
- Priority: High
- CVSS: 9.8 (Medium)
- EPSS: 0.0032
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 29, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | exim4 Debian 12.15 (bookworm) | 4.96-15+deb12u9 | [DEBIAN-CVE-2026-40685](https://patchblox.com/security/data/fix/linux/debian-cve-2026-40685.md) | May 15, 2026 |
| Linux | exim4 Debian 13.5 (trixie) | 4.98.2-1+deb13u2 | [DEBIAN-CVE-2026-40685](https://patchblox.com/security/data/fix/linux/debian-cve-2026-40685.md) | May 15, 2026 |
| Linux | exim4 Debian 14 | 4.99.2-1 | [DEBIAN-CVE-2026-40685](https://patchblox.com/security/data/fix/linux/debian-cve-2026-40685.md) | May 15, 2026 |
| Linux | exim4 Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.12+esm1 | [exim4 4.93-13ubuntu1.12+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-exim4-4.93-13ubuntu1.12-esm1.md) | Jun 24, 2026 |
| Linux | exim4 Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.7 | [exim4 4.95-4ubuntu2.7](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-exim4-4.95-4ubuntu2.7.md) | May 15, 2026 |
| Linux | exim4 Ubuntu 24.04.5 LTS (noble) | 4.97-4ubuntu4.4 | [exim4 4.97-4ubuntu4.4](https://patchblox.com/security/data/fix/linux/ubuntu-noble-exim4-4.97-4ubuntu4.4.md) | May 15, 2026 |
| Linux | exim4 Ubuntu 25.10 (questing) | 4.98.2-1ubuntu2.1 | [exim4 4.98.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-exim4-4.98.2-1ubuntu2.1.md) | May 15, 2026 |
| Linux | exim4 Ubuntu 26.04.1 LTS (resolute) | 4.99.1-1ubuntu1.1 | [exim4 4.99.1-1ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-exim4-4.99.1-1ubuntu1.1.md) | Apr 29, 2026 |
| Linux | exim4-base Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.12+esm1 | [exim4-base 4.93-13ubuntu1.12+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-exim4-base-4.93-13ubuntu1.12-esm1.md) | Jun 24, 2026 |
| Linux | exim4-base Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.7 | [exim4-base 4.95-4ubuntu2.7](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-exim4-base-4.95-4ubuntu2.7.md) | May 15, 2026 |
| Linux | exim4-base Ubuntu 24.04.5 LTS (noble) | 4.97-4ubuntu4.4 | [exim4-base 4.97-4ubuntu4.4](https://patchblox.com/security/data/fix/linux/ubuntu-noble-exim4-base-4.97-4ubuntu4.4.md) | May 15, 2026 |
| Linux | exim4-base Ubuntu 25.10 (questing) | 4.98.2-1ubuntu2.1 | [exim4-base 4.98.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-exim4-base-4.98.2-1ubuntu2.1.md) | May 15, 2026 |
| Linux | exim4-base Ubuntu 26.04.1 LTS (resolute) | 4.99.1-1ubuntu1.1 | [exim4-base 4.99.1-1ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-exim4-base-4.99.1-1ubuntu1.1.md) | Apr 29, 2026 |
| Linux | exim4-config Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.12+esm1 | [exim4-config 4.93-13ubuntu1.12+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-exim4-config-4.93-13ubuntu1.12-esm1.md) | Jun 24, 2026 |
| Linux | exim4-config Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.7 | [exim4-config 4.95-4ubuntu2.7](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-exim4-config-4.95-4ubuntu2.7.md) | May 15, 2026 |
| Linux | exim4-config Ubuntu 24.04.5 LTS (noble) | 4.97-4ubuntu4.4 | [exim4-config 4.97-4ubuntu4.4](https://patchblox.com/security/data/fix/linux/ubuntu-noble-exim4-config-4.97-4ubuntu4.4.md) | May 15, 2026 |
| Linux | exim4-config Ubuntu 25.10 (questing) | 4.98.2-1ubuntu2.1 | [exim4-config 4.98.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-exim4-config-4.98.2-1ubuntu2.1.md) | May 15, 2026 |
| Linux | exim4-config Ubuntu 26.04.1 LTS (resolute) | 4.99.1-1ubuntu1.1 | [exim4-config 4.99.1-1ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-exim4-config-4.99.1-1ubuntu1.1.md) | Apr 29, 2026 |
| Linux | exim4-daemon-heavy Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.12+esm1 | [exim4-daemon-heavy 4.93-13ubuntu1.12+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-exim4-daemon-heavy-4.93-13ubuntu1.12-esm1.md) | Jun 24, 2026 |
| Linux | exim4-daemon-heavy Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.7 | [exim4-daemon-heavy 4.95-4ubuntu2.7](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-exim4-daemon-heavy-4.95-4ubuntu2.7.md) | May 15, 2026 |
| Linux | exim4-daemon-heavy Ubuntu 24.04.5 LTS (noble) | 4.97-4ubuntu4.4 | [exim4-daemon-heavy 4.97-4ubuntu4.4](https://patchblox.com/security/data/fix/linux/ubuntu-noble-exim4-daemon-heavy-4.97-4ubuntu4.4.md) | May 15, 2026 |
| Linux | exim4-daemon-heavy Ubuntu 25.10 (questing) | 4.98.2-1ubuntu2.1 | [exim4-daemon-heavy 4.98.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-exim4-daemon-heavy-4.98.2-1ubuntu2.1.md) | May 15, 2026 |
| Linux | exim4-daemon-heavy Ubuntu 26.04.1 LTS (resolute) | 4.99.1-1ubuntu1.1 | [exim4-daemon-heavy 4.99.1-1ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-exim4-daemon-heavy-4.99.1-1ubuntu1.1.md) | Apr 29, 2026 |
| Linux | exim4-daemon-light Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.12+esm1 | [exim4-daemon-light 4.93-13ubuntu1.12+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-exim4-daemon-light-4.93-13ubuntu1.12-esm1.md) | Jun 24, 2026 |
| Linux | exim4-daemon-light Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.7 | [exim4-daemon-light 4.95-4ubuntu2.7](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-exim4-daemon-light-4.95-4ubuntu2.7.md) | May 15, 2026 |
| Linux | exim4-daemon-light Ubuntu 24.04.5 LTS (noble) | 4.97-4ubuntu4.4 | [exim4-daemon-light 4.97-4ubuntu4.4](https://patchblox.com/security/data/fix/linux/ubuntu-noble-exim4-daemon-light-4.97-4ubuntu4.4.md) | May 15, 2026 |
| Linux | exim4-daemon-light Ubuntu 25.10 (questing) | 4.98.2-1ubuntu2.1 | [exim4-daemon-light 4.98.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-exim4-daemon-light-4.98.2-1ubuntu2.1.md) | May 15, 2026 |
| Linux | exim4-daemon-light Ubuntu 26.04.1 LTS (resolute) | 4.99.1-1ubuntu1.1 | [exim4-daemon-light 4.99.1-1ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-exim4-daemon-light-4.99.1-1ubuntu1.1.md) | Apr 29, 2026 |
| Linux | eximon4 Ubuntu 20.04 LTS (focal) | 4.93-13ubuntu1.12+esm1 | [eximon4 4.93-13ubuntu1.12+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-eximon4-4.93-13ubuntu1.12-esm1.md) | Jun 24, 2026 |
| Linux | eximon4 Ubuntu 22.04.1 LTS (jammy) | 4.95-4ubuntu2.7 | [eximon4 4.95-4ubuntu2.7](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-eximon4-4.95-4ubuntu2.7.md) | May 15, 2026 |
| Linux | eximon4 Ubuntu 24.04.5 LTS (noble) | 4.97-4ubuntu4.4 | [eximon4 4.97-4ubuntu4.4](https://patchblox.com/security/data/fix/linux/ubuntu-noble-eximon4-4.97-4ubuntu4.4.md) | May 15, 2026 |
| Linux | eximon4 Ubuntu 25.10 (questing) | 4.98.2-1ubuntu2.1 | [eximon4 4.98.2-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-eximon4-4.98.2-1ubuntu2.1.md) | May 15, 2026 |
| Linux | eximon4 Ubuntu 26.04.1 LTS (resolute) | 4.99.1-1ubuntu1.1 | [eximon4 4.99.1-1ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-eximon4-4.99.1-1ubuntu1.1.md) | Apr 29, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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