CVE-2026-100404

Zulip: Guests can read new messages in non-subscribed public channels

CVSS score

6.5

EPSS probability

—

Risk score

0.7

Published

3 h ago

Overview Public Exploits (0)Newsroom Vulnerability Timeline

Patch status has not yet been verified

Resmî kaynaklarda yeterli kanıt bulunamadı. Bu sonuç “yama yok” anlamına gelmez.

Impact on My Inventory

Only the personal products you have added to your account are assessed; an organisation's inventory does not appear here.

Checking session…

Vulnerability description

CVE AI research

The stored explanation is shown at once; refreshing evaluates the sources again.

DayBreach AI Explanation

Verified against sources

CVE-2026-100404: Zulip Server Missing Authorization Vulnerability

Sources read

Source agreement

Tam uyum

Evidence confidence

%55

Short explanation

Zulip Server through version 12.1 contains a missing authorization vulnerability (CWE-862) that allows guest users to receive new message events for public channels outside their subscriptions, based on S0 and S1 data.

Why does it matter?

This vulnerability allows unauthorized guest users to access messages from public channels they are not subscribed to, leading to potential confidentiality breaches. According to S0 and S1, this issue is resolved in version 12.2.

What should be done?

Upgrade to version 12.2 or later
Follow vendor advisories

Chain of evidence and sources2 verified claims

Zulip Server sürümleri 12.1 ve öncesinde konuk kullanıcılar abone olmadıkları halka açık kanallardan mesaj alabilir.

S0 · daybreach-canonical S1 · nvd

Bu güvenlik açığı sürüm 12.2 ile giderilmiştir.

S0 · daybreach-canonical S1 · nvd

Show the technical text from the sources

Zulip is an open-source team collaboration tool. In Zulip Server versions through 12.1, guest users can receive new message events for public channels outside their subscriptions. A guest can trigger the issue by registering an event queue with parameters that request messages from an unsubscribed public channel, or an existing event queue can remain affected after the guest's access to the channel is removed. The flaw discloses new public-channel messages to the guest. This issue is fixed in version 12.2.

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CWE: CWE-862

Explanation produced with the local gemini-flash-lite-latest model. Numerical metrics and the KEV, patch and exploit statuses are not determined by AI.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-100404 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

ID	VENDOR	PRODUCT	ACTION
1	zulip	zulip	View

Total affected vendors: 1|Products: 1

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCORE	VERSION	SEVERITY	VECTOR	SOURCE
6.5	CVSS V3_1	MEDIUM	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N	CVE CNA
6.5	CVSS V31	MEDIUM	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N	NVD

Patch and Remediation Guide

Solution & Remediation Advisory

Patch status unknown

İncelenen resmî kaynaklarda yama durumu doğrulanamadı. Bu sonuç “yama yok” anlamına gelmez.

Confirm the affected product and version against the source evidence above.

Restrict access to internet-facing services and apply network segmentation.

Until a patch is confirmed, follow the vendor advisory; do not read an unknown status as “no patch”.

Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-100404 is associated with the following CWEs:

CWE-862: Common Weakness Enumeration Entry CWE-862

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-100404 weaknesses.

CAPEC-66: SQL Injection CAPEC-126: Path Traversal CAPEC-28: OS Command Injection

Attack Vector and Accessibility

ExposureAğ üzerinden

PermissionsLow

UserGerekmiyor

Official Sources and Advisories

https://github.com/zulip/zulip/security/advisories/GHSA-5r8f-gq2h-fcgpvendor-advisory https://github.com/zulip/zulip/pull/39913vendor-advisory https://github.com/zulip/zulip/commit/98659a41cb93d4ce329ea14bb0cdfb4b147500bavendor-advisory https://github.com/zulip/zulip/commit/c03db8916456674df3c98614f6f0ef8cd024ef11vendor-advisory https://github.com/zulip/zulip/releases/tag/12.2vendor-advisory

CVSS Vector Radar Chart

6.5 / 10

Vulnerability Scoring Details

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow privileges

User InteractionNone required

Confidentiality (Gizlilik)Low

Integrity (Bütünlük)None

Availability (Erişilebilirlik)None

Yama durumu bilinmiyor

İncelenen resmî kaynaklarda yama durumu doğrulanamadı. Bu sonuç “yama yok” anlamına gelmez.

Follow the vendor

zulip

Weakness Type (CWE & CAPEC)

CWE-862

Similar Vulnerabilities

9.1

CVE-2026-102893

Get this vulnerability through the API

Affected products, version ranges, exploitation status and patch information in a single request, with a free key.

Get a free key Documentation

curl -H "x-api-key: $DAYBREACH_API_KEY" \
  "https://api.daybreach.dev/api/v1/intel/cves/CVE-2026-100404"