CVE-2023-49105: ownCloud core WebDAV auth bypass via pre-signed URLs

Exploited in the wild Critical 9.8 EPSS 43.2%

ownCloud Server (owncloud/core) 10.6.0 through 10.13.0 accepts pre-signed URLs even when the file owner has no signing key configured, which is the default, so an unauthenticated attacker who knows a username can access, modify or delete any of that user's files over WebDAV (CVSS 9.8). ownCloud fixed it in core 10.13.1 in November 2023 by denying pre-signed URLs when no signing key exists. CISA added it to the Known Exploited Vulnerabilities catalog on 2026-08-27.

CVE-2023-49105CVE identifier
9.8CVSS 3.1 base score (critical)
2026-08-27added to CISA's exploited list (US federal deadline 2026-08-30)
43.2%EPSS: chance of exploitation in the next 30 days (higher than 99% of CVEs)
2023-11-21published

What do these terms mean? CVE · CVSS score · exploited (KEV) · EPSS · backported fix · all terms

What to do now

Check whether you run the affected software and which version (commands below).
Install the fixed version for your system: see “Patch it” below.
Restart the affected service (or reboot for kernel and library updates) so the fix is actually in use.
Because this flaw is being exploited, also check the server for signs of compromise.

Affected and fixed versions

Affected:

ownCloud core 10.6.0 - 10.13.0

Fixed in:

ownCloud core 10.13.1

Am I affected?

sudo -u www-data php occ status

Patch it

Use the commands for your system. Distribution packages often keep an older version number with the fix backported, so compare with the fixed package versions in the table below, not only with the upstream version.

Docker images

docker pull owncloud/server:10.13.1   # or any later 10.x tag
# recreate the container from the new image

Built from source

# Tarball/package installs: upgrade ownCloud Server to 10.13.1 or later following ownCloud's upgrade procedure

General update steps for every system are on the Linux and Unix & BSD pages; after updating, see which services to restart.

CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

https://owncloud.org/security ; https://owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-signed-urls/ ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2023-49105

Sources

Page generated automatically from official sources on 2026-11-03 18:05 UTC and reviewed by an editor. Always confirm with your vendor's advisory.