Medium
Synapse: Invalid device keys degrade federation functionality
Type: advisorySources: OSV
Synapse is an open source Matrix homeserver implementation. Lack of validation for device keys in Synapse before 1.138.3 and in Synapse 1.139.0 allow an attacker registered on the victim homeserver to degrade federation functionality, unpredictably breaking outbound federation to other homeservers. The issue is patched in Synapse 1.138.3, 1.138.4, 1.139.1, and 1.139.2. Note that even though 1.138.3 and 1.139.1 fix the vulnerability, they inadvertently introduced an unrelated regression. For this reason, the maintainers of Synapse recommend skipping these releases and upgrading straight to 1.138.4 and 1.139.2.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2025-61672
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 02:33 UTC · Revision 1
Source evidence
Synapse: Invalid device keys degrade federation functionality
core-osv · Original sourcePublished 8 Oct 2025, 14:55 UTC
Synapse is an open source Matrix homeserver implementation. Lack of validation for device keys in Synapse before 1.138.3 and in Synapse 1.139.0 allow an attacker registered on the victim homeserver to degrade federation functionality, unpredictably breaking outbound federation to other homeservers. The issue is patched in Synapse 1.138.3, 1.138.4, 1.139.1, and 1.139.2. Note that even though 1.138.3 and 1.139.1 fix the vulnerability, they inadvertently introduced an unrelated regression. For this reason, the maintainers of Synapse recommend skipping these releases and upgrading straight to 1.138.4 and 1.139.2.
osv:CVE-2025-61672
Complete source record
{
"id": "e62262e3ae0232d8fa57ff9055c7d33ce07de7c14224c1358450fa30f484c5fc",
"url": "https://osv.dev/vulnerability/CVE-2025-61672",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Synapse: Invalid device keys degrade federation functionality",
"summary": "Synapse is an open source Matrix homeserver implementation. Lack of validation for device keys in Synapse before 1.138.3 and in Synapse 1.139.0 allow an attacker registered on the victim homeserver to degrade federation functionality, unpredictably breaking outbound federation to other homeservers. The issue is patched in Synapse 1.138.3, 1.138.4, 1.139.1, and 1.139.2. Note that even though 1.138.3 and 1.139.1 fix the vulnerability, they inadvertently introduced an unrelated regression. For this reason, the maintainers of Synapse recommend skipping these releases and upgrading straight to 1.138.4 and 1.139.2.",
"evidence": "osv:CVE-2025-61672",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2025-61672",
"aliases": [
"CVE-2025-61672",
"GHSA-fh66-fcv5-jjfr",
"PYSEC-2026-1612"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N"
}
],
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{
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"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-61672.json"
}
}
],
"modified": "2026-10-28T02:30:25.508694748Z",
"provider": "osv",
"references": [
"https://github.com/element-hq/synapse/releases/tag/v1.138.3",
"https://github.com/element-hq/synapse/releases/tag/v1.139.1",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/61xxx/CVE-2025-61672.json",
"https://github.com/element-hq/synapse/security/advisories/GHSA-fh66-fcv5-jjfr",
"https://nvd.nist.gov/vuln/detail/CVE-2025-61672",
"https://github.com/element-hq/synapse/commit/26aaaf9e48fff80cf67a20c691c75d670034b3c1",
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"https://github.com/element-hq/synapse/pull/17097"
],
"provider_metadata": {
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],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/61xxx/CVE-2025-61672.json"
}
},
"related_cves": [
{
"value": "CVE-2025-61672",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 491919,
"published_at": "2025-10-08T14:55:06.378+00:00"
}