CVE-2025-34027
Race Condition in Versa-Networks Concerto 11.4.0 – 12.1.1
Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L/E:X/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:XCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2025-34027 is a critical-severity Time-of-check Time-of-use (TOCTOU) Race Condition (CWE-367) vulnerability in Versa-Networks Concerto. Its CVSS base score is 10.0 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Path Interception (T1034); ranked in the top 1% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-25 (Reference Monitor) and AC-3 (Access Enforcement) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
The Versa Concerto SD-WAN orchestration platform contains an authentication bypass vulnerability in its Traefik reverse proxy configuration that exposes administrative endpoints. The Spack upload endpoint can be abused through a Time-of-Check to Time-of-Use write combined with a race condition, enabling path loading manipulation that leads to remote code execution. The flaw affects versions 12.1.2 through 12.2.0, with additional versions potentially impacted, and carries a CVSS 4.0 score of 10.0 under CWE-367.
An unauthenticated attacker with network access can exploit the bypass to reach privileged endpoints and then chain the TOCTOU condition to execute arbitrary code on the orchestration platform. This grants full control over the SD-WAN environment without requiring credentials or user interaction.
Public analysis of the issue is detailed in reporting from ProjectDiscovery, which describes the authentication bypass and RCE chain but does not include vendor patch or mitigation guidance in the referenced materials.
The EPSS score rose from a low baseline to a peak of 0.0763 on 2026-02-25 before receding to the current value of 0.0278, indicating a period of increased exploitation interest after disclosure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-16088
Vulnerability Data
The Versa Concerto SD-WAN orchestration platform is vulnerable to an authentication bypass in the Traefik reverse proxy configuration, allowing at attacker to access administrative endpoints. The Spack upload endpoint can be leveraged for a Time-of-Check to Time-of-Use (TOCTOU) write in…
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combination with a race condition to achieve remote code execution via path loading manipulation, allowing an unauthenticated actor to achieve remote code execution (RCE).This issue is known to affect Concerto from 12.1.2 through 12.2.0. Additional versions may be vulnerable.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V15.4.2V17.2.6
Mitigating Controls (NIST 800-53 r5) AI
A reference monitor that is always invoked and analyzable structurally eliminates the non-atomic check-then-use pattern underlying TOCTOU.
Access enforcement that performs an atomic check-and-use decision directly stops the window in which a TOCTOU race can be exploited.
Process isolation limits the blast radius of a successful TOCTOU exploitation but does not remove the race itself.
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.
Secure SDLC practices directly include coding standards and reviews that prevent TOCTOU race conditions.