Cyber Resilience

CVE-2026-27942

Memory Safety in Naturalintelligence Fast-Xml-Parser ≤ 4.5.4

Memory Safety
Published
26 February 2026
Modified
02 March 2026
Patch / advisory
View advisory
CVSS Score v4 2.7
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:N/VA:L/SC:N/SI:N/SA:N/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:X
EPSS Score 0.0048 39th percentile
Risk Priority 34 floored blend · peak EPSS

Summary

CVE-2026-27942 is a low-severity Classic Buffer Overflow (CWE-120) vulnerability in Naturalintelligence Fast-Xml-Parser. Its CVSS base score is 2.7 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 39th 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.

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-2026-27942 is a stack overflow vulnerability (CWE-120) in the fast-xml-parser JavaScript library, which provides XML validation, parsing to JavaScript objects, and XML building from objects without C/C++ dependencies or callbacks. The flaw affects versions prior to 5.3.8 and causes the application to crash when the XML builder is invoked with the preserveOrder option set to true.

With a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), the vulnerability is exploitable remotely over the network with low attack complexity, requiring no privileges, user interaction, or privilege escalation. Any unauthenticated attacker can supply crafted input to the XML builder, triggering a stack overflow that results in denial of service through application termination.

The vulnerability is addressed in fast-xml-parser version 5.3.8. Workarounds include using the XML builder with preserveOrder set to false or validating input data prior to passing it to the builder. Additional details are provided in the GitHub security advisory (GHSA-fj3w-jwp8-x2g3), pull request 791, and fixing commit c13a961910f14986295dd28484eee830fa1a0e8a.

EU & UK References

Vulnerability Data

fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. Prior to version 5.3.8, the application crashes with stack overflow when user use XML builder with…

more

`preserveOrder:true`. Version 5.3.8 fixes the issue. As a workaround, use XML builder with `preserveOrder:false` or check the input data before passing to builder.

CWE(s)
CWE-120

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
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 →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-33349Same product: Naturalintelligence Fast-Xml-Parser
CVE-2026-25128Same product: Naturalintelligence Fast-Xml-Parser
CVE-2026-41650Same product: Naturalintelligence Fast-Xml-Parser
CVE-2026-25896Same product: Naturalintelligence Fast-Xml-Parser
CVE-2024-41818Same product: Naturalintelligence Fast-Xml-Parser
CVE-2023-34104Same product: Naturalintelligence Fast-Xml-Parser
CVE-2026-26278Same product: Naturalintelligence Fast-Xml-Parser
CVE-2026-33036Same product: Naturalintelligence Fast-Xml-Parser
CVE-2025-25900Shared CWE-120
CVE-2026-30006Shared CWE-120

Affected Assets

naturalintelligence
fast-xml-parser
≤ 4.5.4 · 5.0.0 — 5.3.8

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V5.2.1

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and analysis can find missing size checks before deployment.

SI-10 Information Input Validation good match

Input validation directly enforces size checks before buffer copies.

SA-8 Security and Privacy Engineering Principles partial match

Engineering principles require bounds checking and safe buffer handling in design.

SI-16 Memory Protection partial match

Memory protection limits the impact of an overflow once it occurs.

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 development practices directly enforce bounds checking and input validation that prevent classic buffer overflows.

ID.RA-01 partial match
prevents

Vulnerability identification processes such as code review or scanning detect classic buffer overflows before exploitation.

PR.PS-02 partial match
prevents

Routine patching replaces vulnerable code containing unchecked buffer copies with corrected versions.

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.8.28 Secure coding mostly match
prevents

Secure coding directly requires bounds-checked memory operations, addressing the root cause of CWE-120.

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

Security testing in development and acceptance can detect buffer overflows through fuzzing and static analysis, though it does not prevent them at the source.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates processes that can include input validation and bounds checking to prevent buffer overflows.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify input-size validation and safe buffer handling to mitigate classic buffer overflows.

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

Secure system architecture and engineering principles promote defensive coding patterns that reduce the likelihood of unchecked buffer copies.

References