GHSA-6QF2-7X63-MM6V
Vulnerability from github – Published: 2026-05-14 16:18 – Updated: 2026-06-09 10:18Impact
In federated rooms, malicious homeservers can craft room events in such a way that prevents Synapse from providing full history to paginating clients.
Clients could therefore fail to display room history.
Patches
Update to Synapse 1.152.1 or later.
Workarounds
There are no known workarounds for this issue.
Identifiers
- ELEMENTSEC-2025-1636
For more information
If you have any questions or comments about this advisory, please email us at security at element.io.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "matrix-synapse"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.152.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-45076"
],
"database_specific": {
"cwe_ids": [
"CWE-20"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-14T16:18:46Z",
"nvd_published_at": "2026-05-28T17:16:31Z",
"severity": "MODERATE"
},
"details": "### Impact\n\nIn federated rooms, malicious homeservers can craft room events in such a way that prevents Synapse from providing full history to paginating clients.\n\nClients could therefore fail to display room history.\n\n### Patches\n\nUpdate to Synapse 1.152.1 or later.\n\n### Workarounds\n\nThere are no known workarounds for this issue.\n\n### Identifiers\n\n- ELEMENTSEC-2025-1636\n\n### For more information\n\nIf you have any questions or comments about this advisory, please email us at [security at element.io](mailto:security@element.io).",
"id": "GHSA-6qf2-7x63-mm6v",
"modified": "2026-06-09T10:18:35Z",
"published": "2026-05-14T16:18:46Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/security/advisories/GHSA-6qf2-7x63-mm6v"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45076"
},
{
"type": "PACKAGE",
"url": "https://github.com/element-hq/synapse"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2026-194.yaml"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Synapse pagination Denial of Service"
}
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| Author | Source | Type | Date | Other |
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Nomenclature
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- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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