Read the docs
TI-2023-08909 Aliases CVE-2023-22735

User uploads proxied from S3 lack `Content-Security-Policy` headers, may be served with…

Priority LOW 22CWE-436Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
Required
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
Low · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA.

Summary

Zulip is an open-source team collaboration tool. In versions of zulip prior to commit `2f6c5a8` but after commit `04cf68b` users could upload files with arbitrary `Content-Type` which would be served from the Zulip hostname with `Content-Disposition: inline` and no `Content-Security-Policy` header, allowing them to trick other users into executing arbitrary Javascript in the context of the Zulip application. Among other things, this enables session theft. Only deployments which use the S3 storage (not the local-disk storage) are affected, and only deployments which deployed commit 04cf68b45ebb5c03247a0d6453e35ffc175d55da, which has only been in `main`, not any numbered release. Users affected should upgrade from main again to deploy this fix. Switching from S3 storage to the local-disk storage would nominally mitigate this, but is likely more involved than upgrading to the latest `main` which addresses the issue.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00515 44th percentileScored 2026-11-07
Fix Fixed zulip (zulip): 2f6c5a8

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
zulipzulip04cf68b to before 2f6c5a82f6c5a8Patch availableCNA
  • zulip Vendorzulip Affected 04cf68b to before 2f6c5a8 Fixed in 2f6c5a8 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:zulip:zulip_server:2023-01-09:*:*:*:*:*:*:*2023-01-09Vulnerablezulip
  • cpe:2.3:a:zulip:zulip_server:2023-01-09:*:*:*:*:*:*:* Versions 2023-01-09 Vulnerable ·zulip

Remediation

  • Fix · CNA zulip (zulip) Fixed in 2f6c5a8

Timeline

  1. 2026-10-02 Threatist record created from CVE-2023-22735

References

Patch 2

Other 2

  • TI-2024-37129 /api/v1/jwt/fetch_api_key endpoint can leak if an email address has an account in Zulip server CVSS 4.0MEDIUM 6.9
  • TI-2022-06082 Multi-use invitations can grant access to other organizations in Zulip CVSS 3.1CRITICAL 9.8
  • TI-2019-13649 In Zulip Server versions from 1.7.0 to before 2.0.7, a bug in the new user signup process… CVSS 3.1CRITICAL 9.8
  • TI-2025-22659 Zulip Authentication Backend Configuration Bypass CVSS 3.1HIGH 8.2
  • TI-2024-24345 Zulip from 8.0 to 8.3 contains a memory leak vulnerability in the handling of popovers. CVSS 3.1HIGH 7.5
  • TI-2020-11848 Zulip Server 2.x before 2.1.7 allows eval injection if a privileged attacker were able to… CVSS 3.1HIGH 8.8
See all 39 →

Sources

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