Cyber Resilience

CVE-2025-13751

DoS in Openvpn 2.5.0 – 2.6.17

Published
03 December 2025
Modified
30 January 2026
Patch / advisory
CVSS Score v4 1.3
Click a component to see what it means
Raw vectorCVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Clear
EPSS Score 0.0017 6th percentile
Risk Priority 15 floored blend · peak EPSS

Summary

CVE-2025-13751 is a low-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Openvpn Openvpn. Its CVSS base score is 1.3 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Network Denial of Service (T1498); ranked at the 6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to AC-10 (Concurrent Session Control) and SA-11 (Developer Testing and Evaluation) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

Interactive service agent in OpenVPN version 2.5.0 through 2.6.16 and 2.7_alpha1 through 2.7_rc2 on Windows allows a local authenticated user to connect to the service and trigger an error causing a local denial of service.

CWE(s)

Related Threats

MITRE ATT&CK Enterprise Techniques

T1498 Network Denial of Service Impact
Adversaries may perform Network Denial of Service (DoS) attacks to degrade or block the availability of targeted resources to users.
T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
T1499.003 Application Exhaustion Flood Impact
Adversaries may target resource intensive features of applications to cause a denial of service (DoS), denying availability to those applications.
T1498.001 Direct Network Flood Impact
Adversaries may attempt to cause a denial of service (DoS) by directly sending a high-volume of network traffic to a target.
T1498.002 Reflection Amplification Impact
Adversaries may attempt to cause a denial of service (DoS) by reflecting a high-volume of network traffic to a target.
T1499.001 OS Exhaustion Flood Impact
Adversaries may launch a denial of service (DoS) attack targeting an endpoint's operating system (OS).
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-4877Same product: Microsoft Windows
CVE-2026-13698Same product: Openvpn Openvpn
CVE-2023-38543Same product: Microsoft Windows
CVE-2025-27556Same product: Microsoft Windows
CVE-2024-28882Same product: Openvpn Openvpn
CVE-2026-12932Same product: Openvpn Openvpn
CVE-2025-36171Same product: Microsoft Windows
CVE-2026-35058Same product: Openvpn Openvpn
CVE-2026-13122Same product: Openvpn Openvpn
CVE-2025-2704Same product: Openvpn Openvpn

Affected Assets

openvpn
openvpn
2.7 · 2.5.0 — 2.6.17

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

Detect
Catch it (NIST detect / respond)

Harden
Shrink the surface (DISA STIG)
  • 5 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V15.4.4
  • V7.2.1

Mitigating Controls (NIST 800-53 r5) AI

Directly enforces a hard limit on concurrent sessions, structurally preventing unbounded resource allocation.

Developer testing and evaluation can discover unreleased descriptors but does not itself enforce their release.

Requires explicit allocation of resources by priority or quota, directly stopping unlimited allocation.

Access enforcement can require each successive workflow step to present the proper authorization context before proceeding.

Imposes a limit on consecutive invalid attempts, preventing one specific class of unbounded resource consumption.

Re-authentication requirements can be placed at critical workflow steps to ensure the actor has performed prior behaviors.

Mitigating Controls (NIST CSF 2.0) AI

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

PR.IR-04 mostly match
degrades

Monitoring capacity and taking action to maintain availability directly reduces unchecked resource allocation.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly enforce proper resource release (e.g., file handles) in code.

PR.AA-05 partial match
prevents

Enforcing authorization policies can include sequence constraints on multi-step actions.

PR.PS-01 partial match
prevents

Hardened configuration baselines can embed required workflow ordering rules.

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.

finds

Baseline comparison of CPU, memory and bandwidth usage helps surface uncontrolled resource allocations before they cause service degradation.

finds

Security testing can detect unreleased descriptors, providing partial coverage of the weakness.

prevents

Capacity projections and elasticity measures ensure that allocation requests are bounded and can be throttled, reducing the window in which an attacker can force unbounded resource reservations.

degrades

Explicit deletion of information assets can include closing file descriptors, but does not mandate it at the code level.

mitigates

Defining retention periods and deletion schedules for backup copies prevents indefinite accumulation of data on storage media without corresponding resource-management controls.

mitigates

Architectural redundancy and automatic failover limit the impact of an attacker who forces excessive allocations, because spare capacity can absorb the load until the primary instance recovers.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (2 rules)
  • V-248552 OL 8 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. prevents CWE-770
  • V-248553 OL 8 must be configured so that all network connections associated with SSH traffic are terminated after 10 minutes of becoming unresponsive. prevents CWE-770
Oracle Linux 9 (2 rules)
  • V-271710 OL 9 must be configured so that all network connections associated with SSH traffic are terminated after 10 minutes of becoming unresponsive. prevents CWE-770
  • V-271709 OL 9 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. prevents CWE-770
RHEL 8 (1 rule)
  • V-230244 RHEL 8 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. prevents CWE-770

References