Security Resilience

CVE-2023-49791

Auth Bypass in Nextcloud Server 23.0.0 – 23.0.12.13

Published
22 December 2023
Modified
21 November 2024
Patch / advisory
CVSS Score v3.1 5.4
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
EPSS Score 0.0061 48th percentile
Risk Priority 44 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2023-49791 is a medium-severity Improper Access Control (CWE-284) vulnerability in Nextcloud Nextcloud Server. Its CVSS base score is 5.4 (Medium).

Operationally, ranked at the 48th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

Nextcloud Server provides data storage for Nextcloud, an open source cloud platform. In Nextcloud Server prior to versions 26.0.9 and 27.1.4; as well as Nextcloud Enterprise Server prior to versions 23.0.12.13, 24.0.12.9, 25.0.13.4, 26.0.9, and 27.1.4; when an attacker manages…

more

to get access to an active session of another user via another way, they could delete and modify workflows by sending calls directly to the API bypassing the password confirmation shown in the UI. Nextcloud Server versions 26.0.9 and 27.1.4 and Nextcloud Enterprise Server versions 23.0.12.13, 24.0.12.9, 25.0.13.4, 26.0.9, and 27.1.4 contain a patch for this issue. No known workarounds are available.

CWE(s)

Related Threats

CVEs Like This One

CVE-2023-28844Same product: Nextcloud Nextcloud Server
CVE-2024-37884Same product: Nextcloud Nextcloud Server
CVE-2023-39962Same product: Nextcloud Nextcloud Server
CVE-2024-37887Same product: Nextcloud Nextcloud Server
CVE-2024-52514Same product: Nextcloud Nextcloud Server
CVE-2023-48303Same product: Nextcloud Nextcloud Server
CVE-2026-45282Same product: Nextcloud Nextcloud Server
CVE-2023-35927Same product: Nextcloud Nextcloud Server
CVE-2023-48239Same product: Nextcloud Nextcloud Server
CVE-2023-39963Same product: Nextcloud Nextcloud Server

Affected Assets

nextcloud
nextcloud server
23.0.0 — 23.0.12.13 · 24.0.0 — 24.0.12.9 · 25.0.0 — 25.0.13.4

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-284 CWE-287

The awareness and training policy mandates training on access control practices, directly reducing the likelihood of improper access control weaknesses being introduced or exploited.

addresses: CWE-284 CWE-287

Training covers access control policies and the consequences of improper access grants or usage by users.

addresses: CWE-284 CWE-287

Security training teaches access control policies and enforcement, reducing improper access control implementations.

addresses: CWE-284 CWE-287

Provides capability to review session content, directly detecting violations of access control.

addresses: CWE-284 CWE-287

System audit review detects violations of access controls by identifying unauthorized access attempts.

addresses: CWE-284 CWE-287

Control assessments verify that access controls are implemented correctly and operating as intended, detecting improper access control before exploitation.

addresses: CWE-284 CWE-287

Requiring formal approval, documented controls, and responsibilities for inter-system exchanges directly enforces proper access control between systems.

addresses: CWE-284 CWE-287

Penetration testing simulates unauthorized access attempts, directly detecting and enabling remediation of improper access control weaknesses.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

blocks

A.5.1 only requires that an information security policy and topic-specific policies (including on access control) exist and are reviewed; it does not itself enforce, implement or act on any access restriction, so the weakness can still be exploited (per the owner's explicit rule that governance/dependency clauses score none on effect verbs).

blocks

A.5.15 directly mandates determining requirements, defining/implementing topic-specific access control policy+rules (with explicit references to 8.3, 5.16, 5.18), and enforcing authorized access while preventing unauthorized access, which squarely stops exploitation of most CWE-284 instances; the bounded remainder is the physical slice (explicitly delegated to 7.2-7.4) plus any second-order defects like path traversal that are not authorization decisions.

blocks

A.5.16's identity lifecycle (unique binding, timely disable/remove, no duplicates, oversight of shared/non-human) directly stops most improper access by ensuring the actor in an access decision is correctly identified and authorized; the bounded remainder is non-identity mechanisms in CWE-284 such as path traversal or CSRF that do not turn on actor identity at all.

blocks

A.5.17 directly mandates generation of non-guessable unique secrets, secure transmission, immediate change of defaults/temporary creds, strong password enforcement, no-reuse, and compromise response, which stops most improper-authentication exploits at source; the bounded remainder is non-password authentication methods and sufficiency-of-proof cases (e.g. IA-2/IA-5 enhancements) left to other controls.

blocks

A.5.18 directly governs the provisioning, review, adjustment and timely revocation of both physical and logical access rights per business rules, segregation of duties and risk-evaluated changes/terminations; this stops most unauthorized-actor exploitation paths named by CWE-284, with a bounded remainder (e.g. path-traversal or CSRF cases that are not authorization decisions at all)

blocks

A.5.2 defines and assigns roles/responsibilities for protection of information and risk acceptance; it does not itself enforce any access decision and cannot stop exploitation of improper access control (per the owner's labeling rule: governance/dependency clauses do not score on prevent/mitigate verbs)

Hardening callouts derived

DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.

  • No fine-grained STIG row for CWE-284, a pillar-level weakness. Rules are authored against its narrower children: CWE-749, CWE-1220.
  • No fine-grained STIG row for CWE-287, a class-level weakness. Rules are authored against its narrower children: CWE-295, CWE-306.

References