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TI-2021-04432 Aliases CVE-2021-21332GHSA-246w-56m2-5899

Cross-site scripting (XSS) vulnerability in the password reset endpoint

Priority LOW 38CWE-79Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Cross-site scripting
Confidentiality · integrity · availability
High · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-79.

Summary

Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.27.0, the password reset endpoint served via Synapse was vulnerable to cross-site scripting (XSS) attacks. The impact depends on the configuration of the domain that Synapse is deployed on, but may allow access to cookies and other browser data, CSRF vulnerabilities, and access to other resources served on the same domain or parent domains. This is fixed in version 1.27.0.

Why it matters now

EPSS 0.01221 68th percentileScored 2026-11-07
Fix Fixed synapse (matrix-org): 1.27.0matrix-synapse (PyPI): 1.27.0

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
matrix-orgsynapsebefore 1.27.01.27.0Patch availableCNA
—matrix-synapse (PyPI)before 1.27.01.27.0Patch availableGHSA-246w-56m2-5899
  • synapse Vendormatrix-org Affected before 1.27.0 Fixed in 1.27.0 Patch available CNA
  • matrix-synapse (PyPI) Vendor— Affected before 1.27.0 Fixed in 1.27.0 Patch available GHSA-246w-56m2-5899

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*before 1.27.0Vulnerablematrix-org
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*34VulnerableFedoraproject
  • cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:* Versions before 1.27.0 Vulnerable ·matrix-org
  • cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* Versions 34 Vulnerable ·Fedoraproject

Remediation

  • Fix · CNA synapse (matrix-org) Fixed in 1.27.0
  • Fix · GHSA-246w-56m2-5899 matrix-synapse (PyPI) Fixed in 1.27.0 Advisory →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-21332
  2. 2026-10-03 Alias added: GHSA-246w-56m2-5899

References

Patch 2

Advisory 4

Other 3

  • TI-2023-15617 Synapse Outgoing federation to specific hosts can be disabled by sending malicious invites CVSS 3.1MEDIUM 5.0
  • TI-2024-35327 Synapse allows a a malformed invite to break the invitee's `/sync` CVSS 4.0HIGH 8.7
  • TI-2019-13571 Matrix Synapse before 1.5.0 mishandles signature checking on some federation APIs. CVSS 3.1CRITICAL 9.8
  • TI-2024-36056 Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders CVSS 4.0HIGH 8.2
  • TI-2024-35318 Synapse allows unsupported content types to lead to memory exhaustion CVSS 4.0HIGH 8.2
  • TI-2018-11846 Matrix Synapse before 0.33.3.1 allows remote attackers to spoof events and possibly have… CVSS 3.0HIGH 8.8
See all 39 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences