Cyber Resilience

CVE-2026-93990

Public PoC
Published
19 September 2026
Modified
28 September 2026
CVSS Score v4 8.7
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/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 0.0037 28th percentile
Risk Priority 45 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-2026-93990 is a high-severity Improper Handling of Unicode Encoding (CWE-176) vulnerability in Hartwork (inferred from references). Its CVSS base score is 8.7 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Obfuscated Files or Information (T1027); ranked at the 28th 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 SI-10 (Information Input Validation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

Expat before 2.8.5 fails to validate that a high surrogate in UTF-16 input is followed by a low surrogate, allowing malformed UTF-16 sequences to be accepted. Attackers can supply UTF-16 encoded XML containing lone high surrogates that consume the following…

more

code unit, causing Expat to pass unpaired surrogates to applications built with XML_UNICODE and to silently replace input characters in other builds.

CWE(s)
CWE-176

Related Threats

MITRE ATT&CK Enterprise Techniques

T1027 Obfuscated Files or Information Stealth
Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system or in transit.
attack.mitre.org →
T1027.018 Invisible Unicode Stealth
Adversaries may abuse invisible or non-printing Unicode characters to conceal malicious content within files, scripts, or text.
attack.mitre.org →
T1132 Data Encoding Command And Control
Adversaries may encode data to make the content of command and control traffic more difficult to detect.
attack.mitre.org →
T1132.002 Non-Standard Encoding Command And Control
Adversaries may encode data with a non-standard data encoding system to make the content of command and control traffic more difficult to detect.
attack.mitre.org →
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.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-25480Shared CWE-176
CVE-2025-71316Shared CWE-176
CVE-2026-4116Shared CWE-176
CVE-2026-35375Shared CWE-176
CVE-2025-55129Shared CWE-176
CVE-2025-59547Shared CWE-176
CVE-2024-8067Shared CWE-176
CVE-2026-20202Shared CWE-176
CVE-2026-35373Shared CWE-176
CVE-2026-4114Shared CWE-176

Affected Assets

Hartwork
—
inferred from references and description; NVD did not file a CPE for this CVE

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation partial match

Input validation directly requires checking and normalizing encodings so that Unicode is handled consistently before further processing.

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 partial match
prevents

Secure SDLC practices directly require proper Unicode/input validation to prevent this weakness.

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.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and encoding handling that can prevent Unicode mishandling.

A.8.26 Application security requirements partial match
prevents

Application security requirements include proper handling of character encodings and input sanitization.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles require robust input processing to avoid encoding-related vulnerabilities.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly address proper Unicode and character-encoding validation.

A.8.29 Security testing in development and acceptance partial match
finds

Security testing can detect Unicode-handling flaws before deployment.

References