Apache CouchDB: Missing authorisation in prefixed _users and _replicator databases
Summary
Apache CouchDB 3.5.2 and earlier, on all platforms, contains missing authorisation checks in the chttpd component. An unauthenticated attacker can send a request to an unauthorised API endpoint and read the full contents of a prefixed _users or _replicator database. Exposure requires such prefixed system databases to exist, which is rare; the data may include password hashes and replication credentials.
Affected
- Apache CouchDB 3.5.2 and earlier, all platforms
- Default installations are unaffected (per the CVE record)
Fixed in
- Apache CouchDB 3.5.3
Workaround
Unknown. No vendor workaround is published. As generic hardening, restrict network access to the CouchDB HTTP API to trusted hosts using firewall or reverse-proxy rules.
Exploitation
- No known exploitation recorded; not listed in CISA KEV (not independently confirmed)
- No public proof of concept found
- CISA SSVC: Exploitation none, Automatable no, Technical Impact total
Our recommendation
- Upgrade all CouchDB instances to 3.5.3 or later
- Check whether prefixed _users or _replicator databases exist; these are the exposed case
- Restrict network access to the CouchDB API, especially from the internet or untrusted networks
- Review access logs for unexpected requests to the API if exposure is suspected
- Note: CVSS scores differ by source; the CVE record gives 8.1 (High, CVSS 4.0)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Apache mailing list thread lists.apache.org
- Apache mailing list thread lists.apache.org
- oss-security mailing list (2026/10/20) www.openwall.com
- OpenCVE entry CVE-2026-90800 app.opencve.io
- Strix CVE-2026-90800 www.strix.ai
- Mallory: CouchDB 3.5.3 release mallory.ai
- CouchDB security documentation docs.couchdb.org
- VulDB entry 422793 vuldb.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 18:40.
Original description (NVD)
Missing authorisation checks in chttpd in Apache CouchDB 3.5.2 and below on all platforms allows any request to read the full contents of a prefixed _user or _replicator database via an unauthorised API endpoint. The use of prefixed system databases is very rare. Users are recommended to upgrade to version 3.5.3, which fixes this issue.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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