# CVE-2026-118673: KeePassXC: Out-of-bounds write in browser integration response encryption with oversized database responses

CVE-2026-118673 is fixed in 2 products on 3 platforms, first by KeePassXC 2.8.0, released October 21, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-118673
- Priority: Routine
- CVSS: 4.1
- EPSS: 0.0012
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 29, 2026
- Weakness: CWE-787: Out-of-bounds Write
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-118673

## Description

KeePassXC is a cross-platform community-driven port of the Windows application KeePass Password Safe. From 2.3.0 until 2.8.0, KeePassXC browser integration encrypts authorized responses in src/browser/BrowserMessageBuilder.cpp using a fixed 1 MiB output vector even though Botan::Sodium::crypto_box_easy() writes the plaintext length plus crypto_box_MACBYTES. A browser-protocol client that can access the per-user IPC endpoint, has a valid database association, and causes an unlocked database to generate and encrypt a sufficiently large authorized response can trigger a sequential out-of-bounds write before any response is delivered. This issue is fixed in version 2.8.0.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | KeePassXC | 2.8.0 | [KeePassXC 2.8.0](https://patchblox.com/security/data/fix/windows-app/keepassxcteam.keepassxc-2.8.0.md) | Oct 21, 2026 |
| macOS | KeePassXC | 2.8.0 | [KeePassXC 2.8.0](https://patchblox.com/security/data/fix/macos/org.keepassxc.keepassxc-2.8.0.md) | Oct 23, 2026 |
| Linux | keepassxc Debian 14 | 2.8.0+dfsg1-1 | [DEBIAN-CVE-2026-118673](https://patchblox.com/security/data/fix/linux/debian-cve-2026-118673.md) | Nov 4, 2026 |

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Data as of 2026-11-09T01:18:40Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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