CVE-2026-103858 MISP Incomplete Thread Authorization Allows Unauthorized Read and Post Access to Discussions
Authenticated users can read and post to restricted MISP discussion threads due to incomplete authorization checks, exposing sensitive data and allowing unauthorized content injection.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-103858?
CVE-2026-103858 is a medium-severity missing authorization vulnerability in MISP, published on 1 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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
Weakness: CWE-285
Which versions are affected by CVE-2026-103858?
How do I fix CVE-2026-103858?
No fix has been published for CVE-2026-103858 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-103858 being exploited?
There is no known exploitation of CVE-2026-103858 in the wild and no public exploit code.
Sources
Also known as GHSA-vwhj-wmrx-p88c.