ownCloud: attackers can get in without a password
OFFICIAL NAME: ownCloud Improper Authentication Vulnerability
WHAT IT IS · DOCUMENTS AND COLLABORATIONIt holds shared documents and internal pages.
DO THIS FIRSTPatch it, or ask your provider whether they have. Not sure if you use it? Send this page to your IT provider or security lead and ask.
TECHNICAL SUMMARY ownCloud contains an improper authentication vulnerability that allows an attacker to access, modify, or delete any file without authentication if the username of a victim is known, and the victim has no signing-key configured.
WHY THIS VERDICT Attacks are confirmed. The severity score is critical (9.8).
- HIGHEST CONFIRMED RUNG
- EXPLOITED
- CISA KEV
- LISTED
- EXPLOIT CODE
- PROOF OF CONCEPT CLAIMED
How far has it climbed?
01 TALK
□ NO EVIDENCE YETNEWEST EVIDENCE NONE YETNo evidence yet.
SRC: NONE YET02 EXPOSED
□ NOT TRACKED YETNO SOURCE FOR THIS STEP YETWe have no source that counts exposed systems yet. Internet scan data needs a partnership we do not have. No evidence here does not mean nothing is exposed.
03 TRIED
■ CONFIRMEDNEWEST EVIDENCE · 2 INDEPENDENT SOURCESAttacks that worked are confirmed (step 4), so attempts count as confirmed too.
04 EXPLOITED
■ CONFIRMEDNEWEST EVIDENCE · 2 INDEPENDENT SOURCESownCloud contains an improper authentication vulnerability that allows an attacker to access, modify, or delete any file without authentication if the username of a victim is known, and the victim has no signing-key configured. CISA Vulnrichment marks CVE-2023-49105 as actively exploited.
05 DAMAGE
□ NOT TRACKED YETNO SOURCE FOR THIS STEP YETBreach notices and filings rarely name the flaw that was used, so we cannot link them to this event yet. No evidence here does not mean no harm.
When each thing happened
- DISCLOSED
- EXPLOIT CODE PUBLICCLAIMED
- FIRST ATTACK REPORT
- CISA KEV LISTING
- US FEDERAL DEADLINE
THE FIX
CISA's instruction: apply the vendor's fix, or stop using the product if no fix exists. The deadline CISA set for US federal agencies, Aug 30, 2026, has passed. It is a US government deadline; use it as a guide.
Questions to ask this week
- Do we run ownCloud? If yes, is it patched or cut off from the internet?
- Who owns fixing it, and by what date?
- Have we checked for signs of attack since the first report, not just since the patch?
How it unfolded
- Attack activity. NOV 20, 2023CISA Vulnrichment marks CVE-2023-49105 as actively exploited
- DEC 5, 20231 public GitHub repository claims a proof of concept for CVE-2023-49105
- Attack activity. AUG 26, 2026ownCloud Improper Authentication Vulnerability
SOURCES
- [1] CISA Known Exploited Vulnerabilities: ownCloud Improper Authentication Vulnerability, AUG 26
- [2] PoC-in-GitHub: 1 public GitHub repository claims a proof of concept for CVE-2023-49105, DEC 5
- [3] CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2023-49105 as actively exploited, NOV 20