Cyber Resilience

CVE-2026-85239

Published
03 September 2026
Modified
03 September 2026
CVSS Score v4 7.1
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/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:X
EPSS Score 0.0024 15th percentile
Risk Priority 35 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-2026-85239 is a high-severity Improper Input Validation (CWE-20) vulnerability. Its CVSS base score is 7.1 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 15th 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 SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

A vulnerability in MISP's event template handling allowed an authenticated user with permission to create or modify event templates to bypass validation of the template definition field. The EventTemplate::beforeValidate() method only performed semantic validation when the supplied definition was already…

more

represented as an array. If a caller instead supplied a pre-encoded string, including malformed JSON or JSON representing an unexpected data type, the value bypassed validateDefinition() and only needed to satisfy the generic notBlank validation rule. As a result, an invalid event template definition could be stored persistently in the database. When event templates were subsequently retrieved, EventTemplate::afterFind() attempted to decode the stored definition using JsonTool::decode() without handling decoding failures. A definition containing invalid JSON could therefore trigger an exception during retrieval. Because the event template index is available to all authenticated users, a single malicious or malformed template could make the event template listing and other functionality relying on EventTemplate queries return HTTP 500 errors until the offending database row was manually repaired. Valid JSON representing an unexpected type, rather than the expected JSON object, could similarly result in invalid data reaching downstream consumers. The vulnerability can therefore be exploited by a user capable of saving event templates to persist malformed template data and cause a persistent denial of service against event-template functionality for other users. The patch enforces that event template definitions must be supplied as structured objects before saving and always applies semantic validation. On retrieval, malformed JSON and definitions that do not decode to the expected structure are caught, logged, and replaced with an empty definition, preventing a malformed database entry from breaking all event template queries. Poisoning doesn't seem reachable according to the lead developer.

CWE(s)

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
T1036.001 Invalid Code Signature Stealth
Adversaries may attempt to mimic features of valid code signatures to increase the chance of deceiving a user, analyst, or tool.
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-0158Shared CWE-20
CVE-2025-32004Shared CWE-20
CVE-2016-6267Shared CWE-20
CVE-2026-17929Shared CWE-20
CVE-2023-50694Shared CWE-20
CVE-2023-26095Shared CWE-20
CVE-2026-14095Shared CWE-20
CVE-2024-38033Shared CWE-20
CVE-2026-45076Shared CWE-20
CVE-2026-4755Shared CWE-20

Affected Assets

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

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Detect
Catch it (NIST detect / respond)

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Harden
Shrink the surface (DISA STIG)
  • 6 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)

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Mitigating Controls (NIST 800-53 r5) AI

Developer testing and evaluation can discover missing input validation through analysis or test cases.

SI-10 directly requires validity checks on information inputs, structurally preventing improper or missing validation.

Requiring documented development standards and tools can embed input-validation practices into the engineering process.

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.PS-06 mostly match
prevents

Secure SDLC practices directly require and enforce input validation during development.

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

Testing against a defined set of requirements and using code review plus vulnerability scanning forces validation of inputs and handling of unanticipated conditions, reducing the chance that malformed data will be accepted.

prevents

Secure-coding guidelines and mandatory security testing (including code scans) compel developers to validate and sanitize inputs at design and implementation time, lowering the incidence of malformed or malicious data reaching downstream components.

prevents

Mandating input controls that include integrity checks and input validation ensures that untrusted data is examined before use, blocking the root cause of many injection and malformed-data weaknesses.

prevents

Security-by-design principles explicitly call for data validation and sanitization at every layer, reducing the chance that malformed or malicious input will be processed without scrutiny.

prevents

Requiring language-specific secure coding standards, peer review, SAST and documented mitigation of common programming errors forces validation of all inputs before they are trusted.

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).

RHEL 8 (1 rule)
  • V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-20

References