Medium Access control

CVE-2026-43889 — Outline: Unauthorized Document Publication via Mixed collectionId+documentId Share

Outline is a service that allows for collaborative documentation. Prior to 1.7.0, the shares.create API accepts both collectionId and documentId simultaneously and, when published=false, only verifies read access for each—skipping the "share" permission check. A subsequent shares.update authorizes publication using an OR policy (can share collection OR can share document), so an attacker who holds share permission on one unrelated collection can publish a share that exposes an arbitrary document they cannot legitimately share, making it publicly accessible to unauthenticated users. This vulnerability is fixed in 1.7.0.

Published May 11, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.4% (30-day exploitation probability)+4
Technical severity (medium)+3
CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.35%

ahead of 27% of scored CVEs · Oct 14, 2026

Affects

Outline

CVSS base

6.5

Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Outline Outline).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (access control), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Outline	Outline	version < 1.7.0	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
6.5	CVSS 3.1	Medium	2.8	3.6	security-advisories@github.com via NIST National Vulnerability Database
6.5	CVSS 3.1	Medium	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-863 · Incorrect Authorization

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.35%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Audit administrative actions and access to resources outside each user’s normal pattern.

web/proxy/WAF logsnetwork IDS/IPSauthentication logsapplication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · outline/outline
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 6.5
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Deferred
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
May 11, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

github.com/outline/outline/security/advisories/GHSA-rg4j-pmch-w6pm
x_refsource_CONFIRM, NIST National Vulnerability Database

Elsewhere on this site

Outline
every CVE for this vendor

Access control
same class

CWE-863
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-54573 Authorization Bypass in API Key/OAuth Scopes via Path Parsing Discrepancy Jun 25, 2026
Medium CVE-2026-44695 Outline: Slack OAuth state can link a victim Outline account to an attacker Slack identity May 11, 2026
High CVE-2026-43886 Outline: OAuth Scope Validation Logic Error Allows Privilege Escalation to Wildcard API Access May 11, 2026
High CVE-2026-43890 Outline: IDOR in subscriptions.create allows cross-tenant subscription on private documents (sibling of GHSA-23jj-rp48-w7q7) May 11, 2026
High CVE-2026-43888 Outline: Zip Extraction Path Escape via PATH_MAX Truncation in Collection Import May 11, 2026
High CVE-2026-43887 Outline: Stored XSS via Comment Mentions May 11, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-43889 is "Outline: Unauthorized Document Publication via Mixed collectionId+documentId Share", rated Medium. It affects Outline (Outline); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.5 describes technical severity. EPSS 0.35% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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