---
id: "CVE-2026-118673"
kind: "vulnerability"
aliases: ["CVE-2026-118673"]
title: "KeePassXC: browser integration heap overflow on large encrypted responses"
severity: "medium"
cvss: 4.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["browser-integration", "desktop", "keepassxc", "package", "password-manager"]
not_affected_if: ["browser-integration-disabled", "version-2.8.0-or-later"]
published_at: "2026-10-29T16:18:03+00:00"
first_seen_at: "2026-10-29T16:25:57+00:00"
updated_at: "2026-10-29T16:32:08+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118673", "first_seen_at": "2026-10-29T16:25:57+00:00"}]
---

# KeePassXC: browser integration heap overflow on large encrypted responses

KeePassXC's browser integration writes encrypted responses into a fixed 1 MiB buffer without checking the size, so an oversized response overflows it. A local browser-protocol client with a valid database association can trigger an out-of-bounds write that may let it affect the running password manager.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed KeePassXC version (Help > About, or `keepassxc --version`); versions from 2.3.0 up to but not including 2.8.0 are affected
- Check whether browser integration is enabled in KeePassXC settings (unknown whether this is the default)

## Fix

- Move KeePassXC to `2.8.0` or later

## Timeline

- 2026-10-29T16:25:57+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118673

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_