CVE-2021-41281: Matrix synapse Path Traversal Vulnerability
HIGHCVE-2021-41281 is a HIGH (CVSS 7.5) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Matrix synapse libraries in the PyPI ecosystem. The issue involves path traversal in matrix synapse. Remediation is available by upgrading affected packages to version 1.47.1.
CVE-2021-41281 at a Glance
Security Impact
CVSS: 7.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N).
How to Fix CVE-2021-41281
To remediate this vulnerability, upgrade all affected Matrix synapse dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
pip install matrix-synapse>=1.47.1Run the following command in your project directory to verify that all resolved dependencies use the patched release:
pip show matrix-synapseHow to Check if You Are Affected
To determine whether your Python environment is affected by CVE-2021-41281, inspect your installed packages using pip:
pip show matrix-synapseAnalyze the terminal output to locate any version of Matrix synapse in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.47.1), your application is affected.
Note: The pip show matrix-synapse command checks currently installed packages in your active Python environment.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Matrix synapse, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2021-41281 Affected Matrix synapse Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
matrix-synapse
|
PyPI |
< 1.47.1
|
1.47.1
|
References
Frequently Asked Questions
What is CVE-2021-41281?
Which Matrix synapse versions are affected?
What version fixes CVE-2021-41281?
Is matrix-synapse affected?
What is the CVSS score of CVE-2021-41281?
What CWE is associated with CVE-2021-41281?
How can I check PyPI dependencies for CVE-2021-41281?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-3hfw-x7gx-437c",
"modified" : "2024-09-24T15:47:18Z",
"published" : "2021-11-23T21:58:56Z",
"aliases" : [ "CVE-2021-41281" ],
"summary" : "Path traversal in Matrix Synapse",
"details" : "### Impact\n\nSynapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory, potentially outside the media store directory.\n\nThe last two directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact.\n\nHomeservers with the media repository disabled are unaffected. Homeservers configured with a federation whitelist are also unaffected.\n\n### Patches\nServer administrators should upgrade to 1.47.1 or later.\n\n### Workarounds\nServer administrators using a reverse proxy could, at the expense of losing media functionality, block the following endpoints:\n\n* `/_matrix/media/r0/download/{serverName}/{mediaId}`\n* `/_matrix/media/r0/download/{serverName}/{mediaId}/{fileName}`\n* `/_matrix/media/r0/thumbnail/{serverName}/{mediaId}`\n\nAlternatively, non-containerized deployments can be adapted to use the hardened systemd config, located at `contrib/systemd/override-hardened.conf`.\n\n### References\nn/a\n\n### For more information\n\nIf you have any questions or comments about this advisory, e-mail us at security@matrix.org.\n",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
}, {
"type" : "CVSS_V4",
"score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "PyPI",
"name" : "matrix-synapse"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "1.47.1"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/matrix-org/synapse/security/advisories/GHSA-3hfw-x7gx-437c"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-41281"
}, {
"type" : "WEB",
"url" : "https://github.com/matrix-org/synapse/commit/91f2bd090"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/matrix-org/synapse"
}, {
"type" : "WEB",
"url" : "https://github.com/matrix-org/synapse/releases/tag/v1.47.1"
}, {
"type" : "WEB",
"url" : "https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-436.yaml"
}, {
"type" : "WEB",
"url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/EU7QRE55U4IUEDLKT5IYPWL3UXMELFAS"
}, {
"type" : "WEB",
"url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/N3WY56LCEZ4ZECLWV5KMAXF2PSMUB4F2"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-22" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2021-11-23T18:44:39Z",
"nvd_published_at" : "2021-11-23T20:15:00Z"
}
}