Medium · CVSS 4.3CVE-2026-46499

Collabora Online: Read-only session authorization bypass permits live document editsCVE-2026-46499

Answer in brief

CVE-2026-46499 records a Medium severity (CVSS 4.3) vulnerability in Collabora Online: Read-only session authorization bypass permits live document edits. The current sources do not mark it as known exploited. The current feed maps CollaboraOnline/online (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 30, 2026Updated Oct 30, 2026Source checked Oct 30, 2026First seen by HOL Oct 30, 2026Material review Oct 30, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 4.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 4.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps CollaboraOnline/online (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
CollaboraOnline/onlinegeneric	<24.04.18 \|\| >=25.04.0-0 <25.04.11	24.04.18, 25.04.11

Recommended response

Check inventory. Check lockfiles and deployed manifests for CollaboraOnline/online.
Review the reported fix. Update CollaboraOnline/online to 24.04.18 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 30, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 30, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 30, 2026

Sources and claim methodology

GitHub security advisorygithub.com

Upstream source description

Collabora Online is a collaborative online office suite based on LibreOffice technology. Prior to 24.04.18 and 25.04.11, several document operations delegated to `LibreOfficeKit` in the per-document kit process fail to enforce a session's read-only state. A read-only user, such as a viewer-role WOPI user, can send crafted `WebSocket` messages to execute document-mutating `UNO` commands and dialog operations despite the read-only interface. The changes can mislead co-viewers within the live session, or an authorized editor sharing the session can unknowingly save the modifications. The read-only attacker cannot save the document directly, and changes are discarded when the kit session ends unless an authorized editor saves them. This issue is fixed in versions 24.04.18 and 25.04.11.

Quoted source text, attributed separately from HOL analysis.

Collabora Online: Reflected HTML injection through host_session_idSame collaboraonline/online package