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TI-2021-16605 Aliases CVE-2021-39220

Bypass of image blocking in Nextcloud Mail

Priority LOW 19CWE-20Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
Required
Attack complexity
Low
Impact type
Information disclosure
Confidentiality · integrity · availability
Low · None · None
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-200.

Summary

Nextcloud is an open-source, self-hosted productivity platform The Nextcloud Mail application prior to versions 1.10.4 and 1.11.0 does by default not render images in emails to not leak the read state or user IP. The privacy filter failed to filter images with a relative protocol. It is recommended that the Nextcloud Mail application is upgraded to 1.10.4 or 1.11.0. There are no known workarounds aside from upgrading.

Why it matters now

EPSS 0.0091 60th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

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

Affected products

VendorProductAffected versionsFixed inStatusSource
nextcloudsecurity-advisories< 1.10.4, < 1.11.0—No fix listedCNA
  • security-advisories Vendornextcloud Affected < 1.10.4, < 1.11.0 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nextcloud:mail:*:*:*:*:*:*:*:*before 1.10.4Vulnerablenextcloud
  • cpe:2.3:a:nextcloud:mail:*:*:*:*:*:*:*:* Versions before 1.10.4 Vulnerable ·nextcloud

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-39220

References

Patch 1

Advisory 1

Other 1

  • TI-2023-09741 Blind SSRF via server URL input in the Nextcloud Mail app CVSS 3.1MEDIUM 5.0
  • TI-2022-13176 Unauthenticated SSRF in 3rd party module "cerdic/csstidy" CVSS 3.1CRITICAL 9.8
  • TI-2023-26170 Nextcloud Mail app vulnerable to Server-Side Request Forgery CVSS 3.1CRITICAL 9.8
  • TI-2021-12320 Missing permission check on email metadata retrieval CVSS 3.1HIGH 8.8
  • TI-2024-35179 Nextcloud Mail auto configurator can be tricked into sending account information to wrong servers CVSS 3.1HIGH 8.2
  • TI-2020-06574 A missing verification of the TLS host in Nextcloud Mail 1.1.3 allowed a man in the middle attack. CVSS 3.1HIGH 7.0
See all 14 →

Sources

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