> ## Content Index > Fetch the complete content index at: https://f4n6.co.uk/llms.txt > Use this file to discover other available public pages before exploring further. # CVE-2023-49105 — ownCloud ownCloud: ownCloud Improper Authentication Vulnerability - URL: https://f4n6.co.uk/security-feed/cve-2023-49105-owncloud-owncloud-owncloud-improper-authentication-vulnerability/ - Published: 2026-08-27T21:10:04.000Z - Updated: 2026-08-27T21:10:04.000Z - Author: Jeff Davies - Tags: #security-feed, CVE-2023-49105 ## 1\. Executive summary CVE-2023-49105 is a critical (CVSS 9.8) improper authentication vulnerability in ownCloud that permits an unauthenticated attacker to access, modify, or delete any file belonging to a victim whose username is known and who has no signing-key configured. The flaw (CWE-287) is now listed in CISA's Known Exploited Vulnerabilities catalogue (added 2026-08-27, EPSS 11%), with a federal remediation due date of 2026-08-30\. EMEA financial services running ownCloud instances with affected configurations face direct risk of unauthenticated data manipulation or exfiltration of sensitive documents. ## 2\. Regulatory framing | Article | Trigger (the fact in this item) | Practical impact | | ------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- | | DORA Art. 24: digital operational resilience testing — general requirements | A CVSS 9.8 unauthenticated file-access vulnerability in a content-collaboration platform requires immediate testing of ownCloud deployments for exposure and signing-key configuration status. | Clients must verify whether their ownCloud instances are affected and test mitigations as part of their operational resilience programme. | | DORA Art. 19: reporting of major ICT-related incidents to competent authorities | Unauthenticated access to files stored in ownCloud could constitute a major ICT-related incident if sensitive financial data is compromised. | If exploitation is detected, clients must classify and report per their DORA incident taxonomy and timelines. | ## 3\. Technical analysis & attack chain **Vulnerability mechanism:** CVE-2023-49105 is an improper authentication flaw (CWE-287) in ownCloud. The vulnerability allows an attacker to bypass authentication entirely when two preconditions are met: (1) the attacker knows the username of a target victim, and (2) the victim has no signing-key configured. Under these conditions, the attacker can access, modify, or delete any file belonging to that user without presenting credentials. ### Attack chain (confirmed steps) 1. **Reconnaissance — username enumeration:** The attacker identifies or guesses valid usernames on the target ownCloud instance. Usernames in ownCloud may be exposed through directory listings, shared-file metadata, or predictable email-address patterns. 2. **Precondition check — signing-key absence:** The vulnerability is exploitable only against accounts that have no signing-key configured. The attacker probes target accounts to determine which lack this control. 3. **Unauthenticated file access:** With a valid username and no signing-key on the target account, the attacker sends requests that bypass the authentication layer, gaining access to the victim's file store. 4. **File manipulation/exfiltration:** The attacker reads, modifies, or deletes files belonging to the victim. The scope of impact is limited to files owned by the targeted user account; lateral access to other users' files depends on per-account exploitation. ### Key technical details - **Component:** ownCloud (product: ownCloud ownCloud) - **CWE:** CWE-287 (Improper Authentication) — listed twice in NVD record - **CVSS:** 9.8 (Critical) — per verified NVD data - **EPSS:** 11% probability of exploitation in the wild - **CISA KEV:** Added 2026-08-27; federal remediation due 2026-08-30 - **Ransomware campaign use:** Unknown (per CISA KEV entry) **Confidence caveat:** The technical description is sourced from the NVD/CISA KEV entry. No vendor advisory, proof-of-concept, or exploit code was provided in the source material. The specific ownCloud versions affected, the exact API endpoint or request structure exploited, and the mechanism by which the signing-key absence enables the bypass are not detailed in the available sources. Verify against the vendor's own security advisory before enforcement. ## 4\. Mitigation & containment ### P1 — Within 24 hours - **Identify exposed ownCloud instances:** Inventory all ownCloud deployments (on-premise, cloud-hosted, third-party-managed). Prioritise internet-facing instances. - **Check signing-key configuration:** Determine which user accounts have no signing-key configured. These accounts are the exploitable population. Enumerate and flag them immediately. - **Restrict external access:** If ownCloud instances are internet-facing, place them behind a VPN or IP-allowlist reverse proxy until mitigations are applied. Block unauthenticated access at the WAF or reverse proxy layer where feasible. - **Review authentication logs:** Search for anomalous unauthenticated file-access patterns targeting known usernames. Look for access events lacking corresponding authentication events. ### P2 — Within 72 hours - **Apply vendor mitigations:** Follow ownCloud vendor instructions for CVE-2023-49105\. Apply patches or configuration changes as specified by the vendor advisory. (The specific patch version was not available in the provided source material — consult the vendor's security channel directly.) - **Enforce signing-key configuration:** Mandate signing-key configuration for all user accounts on ownCloud instances. This eliminates the exploitable precondition. - **Notify affected users:** If exploitation is suspected, notify users whose accounts had no signing-key configured and review their file stores for unauthorised modifications or deletions. ### P3 — Within 7 days - **Harden ownCloud configuration:** Review and enforce authentication hardening across all ownCloud deployments. Ensure signing-key requirements are enforced by policy for new accounts. - **Update asset inventory:** Record ownCloud version, patch level, and signing-key enforcement status in the CMDB. - **BOD 26-04 alignment:** For clients subject to US federal requirements, ensure compliance with CISA BOD 26-04 prioritisation and forensics triage guidance. Evaluate each asset's internet exposure and patch accordingly. ## 5\. Indicators of compromise No indicators of compromise available in the source material. ### Behavioural indicators | Behaviour | Where to observe | Confidence | | ------------------------------------------------------------------------------------- | ------------------------------------------------------------------ | ------------------------------------------------------------------------------------ | | Unauthenticated file-access requests targeting known usernames | ownCloud application logs; WAF/reverse proxy logs | Medium — consistent with vulnerability mechanism but not observed in field reporting | | File access, modification, or deletion events without preceding authentication events | ownCloud audit logs; SIEM correlation of auth + file-access events | Medium — derived from vulnerability description, not from confirmed exploitation | | Enumeration of usernames followed by file-access attempts | ownCloud access logs; WAF logs showing sequential username probing | Low — plausible attack pattern but not described in source material | ## 6\. Detection Insufficient indicators to author detection rules. The source material does not provide specific API endpoints, request patterns, user-agent strings, file paths, or other artefacts that would distinguish exploitation of CVE-2023-49105 from legitimate ownCloud activity. Recommend monitoring ownCloud audit logs for file-access events that lack corresponding authentication events, correlated by username and timestamp, until vendor-specific detection guidance is available. ## CVE assessment 1 referenced CVE — **1 actively exploited (CISA KEV)**, 1 critical (CVSS ≥ 9.0) | CVE | CVSS | Exploited | EPSS | Summary | | -------------------------------------------------------------------------------- | ------------ | ---------------- | ---- | --------------------------------------------------------------------------------------------------------------------------------- | | [CVE-2023-49105](https://nvd.nist.gov/vuln/detail/CVE-2023-49105?ref=f4n6.co.uk) | 9.8 Critical | ⚠ KEV 2026-08-27 | 11% | An issue was discovered in ownCloud owncloud/core before 10.13.1\. An attacker can access, modify, or delete any file without au… | ## 7\. Sources - NVD, "CVE-2023-49105 — ownCloud Improper Authentication Vulnerability," https://nvd.nist.gov/vuln/detail/CVE-2023-49105, published 2026-08-26 - CISA KEV catalogue entry (CVE-2023-49105, added 2026-08-27, due 2026-08-30) — referenced via NVD source ## 8\. Adverse Trace position CVE-2023-49105 is a genuine critical-severity vulnerability (CVSS 9.8, CWE-287) with a low but non-trivial EPSS exploitation probability (11%) and confirmed inclusion in CISA KEV with a near-term remediation deadline of 2026-08-30\. The attack preconditions — known username and absent signing-key — lower the barrier to exploitation compared to a full authentication bypass, making internet-facing ownCloud instances with default or incomplete configurations the primary risk surface. For EMEA financial services, any ownCloud deployment storing sensitive client data, internal financial reports, or regulatory submissions is a priority asset. Attribution to any threat actor is unconfirmed; no MITRE ATT&CK actor profile is linked in the verified reference data. We are treating this as a high-priority patch-and-configure action: clients should identify exposed instances within 24 hours, enforce signing-key configuration as an immediate compensating control, and apply the vendor patch once available. We will update this advisory if vendor technical details, exploit code, or confirmed in-the-wild exploitation reporting emerges. --- [Read the original source →](https://nvd.nist.gov/vuln/detail/CVE-2023-49105?ref=f4n6.co.uk) *Published via PulseTrace — Adverse Trace threat intelligence.*