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

Status: published. Published: 2026-10-29. Updated: 2026-11-03.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- keepassxreboot / keepassxc: >= 2.3.0, < 2.8.0 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 4.0: 4.1 (medium); CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: GitHub_M

- CVSS 4.0: 4.1 (medium); CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: 0.11% as of 2026-11-03; percentile 1.55%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-787

## Exploit evidence

- exploit: https://github.com/keepassxreboot/keepassxc/security/advisories/GHSA-3448-gh8j-3227 (ADP: CISA-ADP)

## References

- https://github.com/keepassxreboot/keepassxc/security/advisories/GHSA-3448-gh8j-3227 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/keepassxreboot/keepassxc/pull/13679 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/keepassxreboot/keepassxc/commit/80e68bb4e8b89e383dd96b1bf5de169ca61367aa (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/keepassxreboot/keepassxc/releases/tag/2.8.0 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/keepassxreboot/keepassxc/security/advisories/GHSA-3448-gh8j-3227 (ADP: CISA-ADP; exploit)

- https://github.com/keepassxreboot/keepassxc/commit/80e68bb4e8b89e383dd96b1bf5de169ca61367aa (security-advisories@github.com)

- https://github.com/keepassxreboot/keepassxc/pull/13679 (security-advisories@github.com)

- https://github.com/keepassxreboot/keepassxc/releases/tag/2.8.0 (security-advisories@github.com)

- https://github.com/keepassxreboot/keepassxc/security/advisories/GHSA-3448-gh8j-3227 (security-advisories@github.com)

- https://github.com/keepassxreboot/keepassxc/security/advisories/GHSA-3448-gh8j-3227 (134c704f-9b21-4f2e-91b3-4a467353bcc0)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-118673; retrieved 2026-11-03; source updated 2026-11-03

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-118673; retrieved 2026-11-03; source updated 2026-11-03

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-118673; retrieved 2026-11-03; source updated Not reported

Revision: c61f9b25a5fd9074d494d8d88b9decca220a2a0a1629c184a4727c7f729a1c5a

Canonical: https://y2.dev/cve/CVE-2026-118673

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- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

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