MISP Incomplete Thread Authorization Allows Unauthorized Read and Post Access to Discussions (CVE-2026-103858) | HOL Guard CVE

Medium · CVSS 5.3CVE-2026-103858

MISP Incomplete Thread Authorization Allows Unauthorized Read and Post Access to Discussions

Answer in brief

CVE-2026-103858 records a Medium severity (CVSS 5.3) vulnerability in MISP Incomplete Thread Authorization Allows Unauthorized Read and Post Access to Discussions. The current sources do not mark it as known exploited. The current feed maps MISP/MISP (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 1, 2026Updated Oct 1, 2026Source checked Oct 1, 2026First seen by HOL Oct 1, 2026Material review Oct 1, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 5.3. 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 MISP/MISP (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
MISP/MISPgeneric	>=unspecified <2.5.48	2.5.48

Recommended response

Check inventory. Check lockfiles and deployed manifests for MISP/MISP.
Review the reported fix. Source-reported solution: The fix replaces the limited org-only distribution check with a call to the thread's full authorization method (checkIfAuthorised), which enforces the complete access control list including sharing groups and event-level visibility. The thread is only read after successful authorization, preventing disclosure of the title and content to unauthorized users. An additional null-check on the post's thread_id was added to prevent referencing posts without a valid thread association.

Evidence timeline and material changes

Published upstream
Oct 1, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 1, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 1, 2026

Sources and claim methodology

GitHub security advisorygithub.com

Upstream source description

MISP contains an incomplete authorization check in the discussion posting functionality. When a user submits a post to a thread or replies to an existing post, the application only verified whether the target thread was restricted to a single organization (org-only distribution). It did not enforce the full thread access control list, including sharing-group membership and event-level visibility. As a result, an authenticated user who is outside the relevant sharing group or who does not have visibility on the associated event could: - Read the thread title and the content of the quoted post - Submit a new post into the discussion thread This constitutes both an information disclosure (reading restricted thread and post content) and an integrity issue (injecting content into a thread the user is not authorized to participate in). Affected: <2.5.48

Quoted source text, attributed separately from HOL analysis.