PYSEC-2026-1612
Vulnerability from pysec - Published: 2026-07-07 16:03 - Updated: 2026-07-07 17:24
VLAI
Details
Impact
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.
Patches
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, it is recommend to skip these releases and upgrading straight to 1.138.4 and 1.139.2.
Workarounds
The vulnerability can only be exploited by users registered on the victim homeserver.
Severity
Impacted products
| Name | purl | matrix-synapse | pkg:pypi/matrix-synapse |
|---|
Aliases
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "matrix-synapse",
"purl": "pkg:pypi/matrix-synapse"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.138.3"
},
{
"introduced": "1.139.0rc2"
},
{
"fixed": "1.139.1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.33.5",
"0.33.5.1",
"0.33.6",
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"0.33.9",
"0.34.0",
"0.34.0.1",
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"0.34.1.1",
"0.99.0",
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]
}
],
"aliases": [
"CVE-2025-61672",
"GHSA-fh66-fcv5-jjfr"
],
"details": "### Impact\n\nLack 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. \n\n### Patches\n\nPatched in Synapse 1.138.3, 1.138.4, 1.139.1, and 1.139.2.\n\nNote that even though 1.138.3 and 1.139.1 fix the vulnerability, they inadvertently introduced an unrelated regression. For this reason, it is recommend to skip these releases and upgrading straight to 1.138.4 and 1.139.2.\n\n### Workarounds\n\nThe vulnerability can only be exploited by users registered on the victim homeserver.",
"id": "PYSEC-2026-1612",
"modified": "2026-07-07T17:24:38.832865Z",
"published": "2026-07-07T16:03:07.105115Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/security/advisories/GHSA-fh66-fcv5-jjfr"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-61672"
},
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/pull/17097"
},
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/commit/26aaaf9e48fff80cf67a20c691c75d670034b3c1"
},
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/commit/7069636c2d6d1ef2022287addf3ed8b919ef2740"
},
{
"type": "PACKAGE",
"url": "https://github.com/element-hq/synapse"
},
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/releases/tag/v1.138.3"
},
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/releases/tag/v1.138.4"
},
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/releases/tag/v1.139.1"
},
{
"type": "WEB",
"url": "https://github.com/element-hq/synapse/releases/tag/v1.139.2"
},
{
"type": "PACKAGE",
"url": "https://pypi.org/project/matrix-synapse"
},
{
"type": "ADVISORY",
"url": "https://github.com/advisories/GHSA-fh66-fcv5-jjfr"
}
],
"severity": [
{
"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",
"type": "CVSS_V4"
}
],
"summary": "Synapse\u0027s invalid device keys degrade federation functionality"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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