CVE-2023-22735 json
User uploads proxied from S3 lack `Content-Security-Policy` headers, may be served with `Content-Disposition: inline` in zulip
published 2023-02-07 3 y ago modified 2026-06-17 4 mo ago also EUVD-2023-26855
- cvss
- 4.4
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 44%
- public exploits
- 0
- none known
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.
Patch / fix
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 19 mo ago
Exploit prediction
0.52% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.4 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N |
| NVD | 3.1 | 4.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N |
Affected products
- zulip zulip
Classification
- Weakness
-
- CWE-436 Interpretation Conflict
References
-
github.com
/zulip/zulip/commit/04cf68b45ebb5c03247a0d6453e35ffc175d55da
product
-
github.com
/zulip/zulip/commit/2f6c5a883e106aa82a570d3d1f243993284b70f3
patch
-
github.com
/zulip/zulip/security/advisories/GHSA-wm83-3764-5wqh
patch, vendor-advisory
-
zulip.readthedocs.io
/en/latest/production/upgrade-or-modify.html#upgrading-from-a-git-repository
not-applicable
Sources
- CVE List CVE-2023-22735
- NVD CVE-2023-22735
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