CVE-2026-39911
Hedera Guardian ≤ 3.5.0
Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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-2026-39911 is a high-severity Exposure of Resource to Wrong Sphere (CWE-668) vulnerability in Hedera Guardian. Its CVSS base score is 8.7 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Data from Local System (T1005); ranked at the 44th percentile by exploit likelihood (below the median); 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-3 (Access Enforcement) and AC-4 (Information Flow 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.
CVE-2026-39911 is an unsandboxed JavaScript execution vulnerability in Hashgraph Guardian through version 3.5.1, fixed in commit 45fbe2f. The flaw exists in the Custom Logic policy block worker, which passes user-supplied JavaScript expressions directly to the Node.js Function() constructor without isolation. This affects the software's handling of custom logic policies for authenticated Standard Registry users.
Authenticated Standard Registry users can exploit the vulnerability to execute arbitrary code remotely. Attackers can import native Node.js modules to read arbitrary files from the container filesystem, access process environment variables containing sensitive credentials such as RSA private keys, JWT signing keys, and API tokens, and forge valid authentication tokens for any user including administrators. The issue has a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) and maps to CWE-668.
Mitigation is available via the fixing commit at https://github.com/hashgraph/guardian/commit/45fbe2f7e0e8feee30105d42d66ed63fb6177ebe and pull request https://github.com/hashgraph/guardian/pull/5929. Further details on the vulnerability and remediation are provided in the VulnCheck advisory at https://www.vulncheck.com/advisories/hashgraph-guardian-unsandboxed-javascript-execution-rce.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-20993
Vulnerability Data
Hashgraph Guardian through version 3.5.1, fixed in commit 45fbe2f, contains an unsandboxed JavaScript execution vulnerability in the Custom Logic policy block worker that allows authenticated Standard Registry users to execute arbitrary code by passing user-supplied JavaScript expressions directly to the…
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Node.js Function() constructor without isolation. Attackers can import native Node.js modules to read arbitrary files from the container filesystem, access process environment variables containing sensitive credentials such as RSA private keys, JWT signing keys, and API tokens, and forge valid authentication tokens for any user including administrators.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 6 hardening rules · 5 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
Access enforcement directly stops resources from being reachable by actors outside the intended control sphere.
Information flow enforcement structurally prevents unintended cross-sphere data or resource exposure.
Least privilege reduces the set of actors that can reach a resource, limiting wrong-sphere exposure.
Security attributes enable correct sphere assignment and subsequent enforcement decisions.
Boundary protection at interfaces prevents resources from being exposed outside authorized spheres.
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.
Enforcing least-privilege authorizations directly prevents resources from being exposed outside their intended control sphere.
Network segmentation and unauthorized-access protections reduce the chance of resources being reachable by the wrong sphere.
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.
Placing systems of differing trust levels into separate domains prevents resources from being placed in a sphere where they are reachable by unintended actors.
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` (higher-evidence rows only; rows rated `none` are excluded).
Oracle Linux 8 (2 rules)
- V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-668
- V-248823 OL 8 must not have the telnet-server package installed. prevents CWE-668
RHEL 7 (1 rule)
- V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. prevents CWE-668
Windows 10 (1 rule)
- V-220967 The Debug programs user right must only be assigned to the Administrators group. prevents CWE-668
Windows Server 2016 (1 rule)
- V-225079 The Debug programs user right must only be assigned to the Administrators group. prevents CWE-668
Windows Server 2019 (1 rule)
- V-205757 Windows Server 2019 Debug programs: user right must only be assigned to the Administrators group. prevents CWE-668