CriticalCVE-2023-49105

    ownCloud Improper Authentication Vulnerability (CVE-2023-49105)

    Published Last modified In CISA KEV since Sources: BSI, SingCERT, NCSC NZ, CVE.org

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    What is affected, what to do

    The vulnerability CVE-2023-49105 allows an attacker to access, modify, or delete any file in ownCloud without authentication if the victim's username is known and no signing-key is configured. This affects ownCloud versions from 10.6.0 to 10.13.1. The issue arises because pre-signed URLs are accepted even without a signing-key for the file owner. The vulnerability is actively exploited and listed in the CISA KEV catalog. An immediate patch to version 10.13.1 or higher is urgently required to mitigate the risk.

    The vulnerability is being actively exploited; treat it as a priority. Update ownCloud Server to version 10.13.1. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • ownCloud Server lt 10.6.0..10.13.1
    Fixed in
    • ownCloud Server 10.13.1

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: BSI, SingCERT, NCSC NZ, CVE.org

    43.2 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 98.7

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    230.82 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: NCSC NZ How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    43.2 %
    Elevated — model estimates 10-50% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    98.7
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 27 November 2023
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-287

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This CVE sits on KEV because it is pre-authentication, network-reachable, and trivially weaponised once a username is known — and most ownCloud deployments populate speaking usernames (firstname.lastname, email prefix). Exploitation likelihood is accordingly very high; the CVSS vector (AV:N/AC:L/PR:N/UI:N, C:H/I:H/A:H) reflects total loss of file confidentiality, integrity and availability. For NIS2-regulated organisations using ownCloud as a document store, this is a critical confidentiality and integrity risk (GDPR Art. 32, with potential Art. 33 breach-notification duty on confirmed access). Prioritise P1 if ownCloud is internet-facing or holds sensitive data; P2 for purely internal, VPN-fronted deployments, but still patch within the next scheduled window.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade ownCloud Core to 10.13.1 or later — this is the only complete fix. In change-controlled environments, convene an emergency CAB: the flaw is pre-authentication and network-reachable.
      • Until patched, remove all ownCloud instances from the public internet (reverse-proxy deny, WAF block, or VPN-only access). The vulnerability grants unauthenticated full access to any user's files once the username is known, and usernames are usually trivial to guess (email prefix, LDAP sync).
      • Force a signing-key for every user that currently has none via the occ CLI (review the occ security:sign-url workflow). A missing signing-key is the precondition of the bug.
      • Preserve 90 days of access and audit logs (or since the 10.6.0 rollout) offline for forensics on suspicious pre-signed URL requests before deploying the patch.
      • Rotate admin and service accounts (owncloud_admin, backup user) if any evidence of unauthorised file access surfaces. Invalidate session tokens via occ user:resetpassword or by flushing the oc_authtoken database table.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: place the ownCloud web frontend behind a reverse proxy (nginx, HAProxy, Traefik) with IP allowlisting restricted to corporate ranges and VPN pools. Disable direct internet access to port 443 until patched.
      • WAF / reverse-proxy rule: block or at minimum log requests to /remote.php/dav/ and /ocs/ carrying URL parameters OC-Signature, OC-Credential, OC-Expires, OC-Verb when no valid session cookie is present. Signed URLs are a legitimate feature — but untrustworthy pre-patch.
      • Configuration hardening: restrict remote.trusted_servers in config.php and disable Federated Sharing if unused. Suppress username enumeration via /ocs/v1.php/cloud/users through a reverse-proxy rule.
      • IAM hardening: decouple usernames from email addresses (use internal IDs instead of speaking names) to raise the bar on the "username known" precondition. For new deployments, review the LDAP attribute mapping.
      • Filesystem monitoring: watch the ownCloud data directory (/var/www/owncloud/data/) with auditd or AIDE for unexpected read / write / delete operations by the web server user (www-data, apache), particularly outside business hours.
      • Backup validation: verify that point-in-time backups of the ownCloud database and data directory are available — the flaw allows deletion of other users' files without leaving traces in the application log.

    3. Runbook step 3

      Detection rules

      • Webserver access log (nginx / Apache): GET / PUT / DELETE on /remote.php/webdav/ or /remote.php/dav/files/ with a query string containing OC-Signature= and no corresponding authenticated session cookie. Sigma shape: selection: cs-uri-query|contains: 'OC-Signature' AND cs-cookie|not_contains: 'oc_'.
      • High count of HTTP 200 responses to /remote.php/dav/files/<username>/ from a single source IP in a short window (username list enumeration). KQL shape: WebLogs | where UriPath startswith "/remote.php/dav/files/" | summarize dcount(UriPath) by SourceIP, bin(TimeGenerated, 5m) | where dcount_UriPath > 20.
      • ownCloud Auditing app (if installed): events file_accessed, file_deleted, file_changed where user= is empty or user=anonymous on files that are not public shares.
      • auditd on the ownCloud host: watch /var/www/owncloud/data/ with -w /var/www/owncloud/data -p rwxa -k owncloud_data. Alert on DELETE / WRITE by www-data that falls outside normal request patterns.
      • Network telemetry (Zeek / Suricata): HTTP requests carrying URI parameter OC-Signature with an unusually old or far-future OC-Expires timestamp — a tell of hand-crafted pre-signed URLs.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    An issue was discovered in ownCloud owncloud/core before 10.13.1. An attacker can access, modify, or delete any file without authentication if the username of a victim is known, and the victim has no signing-key configured. This occurs because pre-signed URLs can be accepted even when no signing-key is configured for the owner of the files. The earliest affected version is 10.6.0.

    Source: BSI CSAF, BSI WID Portal, CSA/SingCERT, NCSC NZ (CC BY 4.0), CISA KEV Catalog, NVD (NIST), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    owncloudowncloud_server
    • 10.6.0 – < 10.13.1
    • 10.13.1
    ownCloudownCloud
    • < 10.13.1
    • 10.13.1

    Vendors and products

    Weakness classes (CWE)

    • CWE-287Improper Authentication

      Class

      When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

      Entry at MITRE CWE-287

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    NCSC NZThree critical vulnerabilities affecting ownCloud software (opens in a new tab)NCSC NZactively exploited

    References & sources

    • owncloud.orgsecurity
    • owncloud.comsecurity-advisories/webdav-api-authentication-bypass-using-pre-…
    • hunt.ioblog/chinese-speaking-operator-philippine-nuclear-naval-contrac…Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2023-49105government-resource

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. NVD analysis modifiedNVD

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Reference typeadded
      —
      CISA-ADP: https://hunt.io/blog/chinese-speaking-operator-philippine-nuclear-naval-contractor Types: Third Party Advisory
      Reference typeadded
      —
      CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-49105 Types: US Government Resource

      Source identifier: nvd@nist.gov

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: yes

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentchanged
      {"id":"CVE-2023-49105","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-27T17:44:05.938842Z"}
      {"id":"CVE-2023-49105","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2023-11-27T00:00:00+00:00"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    3. Record modifiedMITRE

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-signed-urls/
      Referenceadded
      —
      https://owncloud.org/security
      Referenceremoved
      https://owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-signed-urls/
      —
      Referenceremoved
      https://owncloud.org/security
      —
      Reference typeremoved
      https://owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-signed-urls/ Types: Vendor Advisory
      —
      Reference typeremoved
      https://owncloud.org/security Types: Product
      —

      Source identifier: cve@mitre.org

    4. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: yes

      Weakness type: CWE-287

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-287
      Referenceadded
      —
      https://hunt.io/blog/chinese-speaking-operator-philippine-nuclear-naval-contractor
      Referenceadded
      —
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-49105
      SSVC assessmentchanged
      {"id":"CVE-2023-49105","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2023-11-28T05:00:24.236864Z"}
      {"id":"CVE-2023-49105","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-27T17:44:05.938842Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    5. Record modifiedCVE Program

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-signed-urls/
      Referenceadded
      —
      https://owncloud.org/security
      Referenceremoved
      https://owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-signed-urls/
      —
      Referenceremoved
      https://owncloud.org/security
      —
      Reference typeremoved
      https://owncloud.com/security-advisories/webdav-api-authentication-bypass-using-pre-signed-urls/ Types: Vendor Advisory
      —
      Reference typeremoved
      https://owncloud.org/security Types: Product
      —

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

    Linked advisories

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