Medium
Zulip: Guests can read new messages in non-subscribed public channels
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-100404
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 2 Nov 2026, 16:50 UTC · Revision 1
Source evidence
Zulip: Guests can read new messages in non-subscribed public channels
core-osv · Original sourcePublished 14 Oct 2026, 15:50 UTC
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.
osv:CVE-2026-100404
Complete source record
{
"id": "dbb4f3149b55f61f84ca95d96d25e0110fd9cb35dd111bcb0cad3e3802e00f14",
"url": "https://osv.dev/vulnerability/CVE-2026-100404",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Zulip: Guests can read new messages in non-subscribed public channels",
"summary": "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.",
"evidence": "osv:CVE-2026-100404",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-100404",
"aliases": [
"CVE-2026-100404",
"GHSA-5r8f-gq2h-fcgp"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/zulip/zulip",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "1e73e1d754761b73c18135a3f25d0673f31cd8b3"
},
{
"fixed": "98659a41cb93d4ce329ea14bb0cdfb4b147500ba"
},
{
"fixed": "c03db8916456674df3c98614f6f0ef8cd024ef11"
}
],
"database_specific": {
"extracted_events": [
{
"range": [
{
"introduced": "0"
},
{
"fixed": "12.2"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
},
{
"range": [
{
"fixed": "98659a41cb93d4ce329ea14bb0cdfb4b147500ba"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "c03db8916456674df3c98614f6f0ef8cd024ef11"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "1e73e1d754761b73c18135a3f25d0673f31cd8b3"
}
],
"source": "REFERENCES_TAG",
"original_tag": "12.2"
}
]
}
}
],
"versions": [
"12.1",
"12.0",
"12.0-beta2",
"12.0-beta1",
"12.0-dev",
"11.0",
"11.0-beta2",
"11.0-beta1",
"11.0-dev",
"10.0",
"10.0-beta2",
"10.0-beta1",
"9.0",
"9.0-beta1",
"8.0",
"9.0-dev",
"8.0-beta2",
"8.0-beta1",
"8.0-dev",
"7.0",
"7.0-beta3",
"shared-0.0.18",
"shared-0.0.17",
"7.0-dev",
"6.0",
"shared-0.0.16",
"shared-0.0.15",
"shared-0.0.14",
"shared-0.0.13",
"shared-0.0.12",
"shared-0.0.11",
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"6.0-dev",
"5.0",
"shared-0.0.9",
"shared-0.0.8",
"shared-0.0.7",
"shared-0.0.6",
"4.0",
"5.0-dev",
"shared-0.0.5",
"shared-0.0.4",
"shared-0.0.3",
"4.0-dev",
"3.0",
"3.0-rc2",
"3.0-rc1",
"3.0-dev",
"2.2-dev",
"2.1.0",
"2.1.0-rc1",
"shared-0.0.2",
"shared-0.0.1",
"2.0.0",
"2.1-dev",
"2.0.0-rc1",
"1.9.0",
"1.9.0-rc3",
"1.9.0-rc2",
"1.8.0",
"1.8.0-rc1",
"1.7.0",
"1.6.0",
"1.5.0",
"1.4.0",
"1.3.13",
"1.3.11",
"1.3.10",
"1.3.9",
"1.3.8",
"1.3.7",
"1.3.6",
"1.3.5",
"1.3.4",
"1.3.3",
"1.3.2",
"1.3.1",
"1.3.0",
"enterprise-1.2.0",
"enterprise-1.1.5"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-100404.json"
}
}
],
"modified": "2026-10-31T02:30:34.924536092Z",
"provider": "osv",
"references": [
"https://github.com/zulip/zulip/releases/tag/12.2",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100404.json",
"https://github.com/zulip/zulip/security/advisories/GHSA-5r8f-gq2h-fcgp",
"https://nvd.nist.gov/vuln/detail/CVE-2026-100404",
"https://github.com/zulip/zulip/commit/98659a41cb93d4ce329ea14bb0cdfb4b147500ba",
"https://github.com/zulip/zulip/commit/c03db8916456674df3c98614f6f0ef8cd024ef11",
"https://github.com/zulip/zulip/pull/39913"
],
"provider_metadata": {
"cwe_ids": [
"CWE-862"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100404.json"
}
},
"related_cves": [
{
"value": "CVE-2026-100404",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 487391,
"published_at": "2026-10-14T15:50:00.354+00:00"
}