CVE-2026-0821

HighPublic PoC

Published: 10 January 2026

Published

10 January 2026

Modified

23 February 2026

KEV Added

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Patch

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CVSS Score 7.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

EPSS Score 0.0017 38.3th percentile

Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-0821 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Quickjs-Ng Quickjs. Its CVSS base score is 7.3 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 38.3th 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 are NIST 800-53 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Requires timely identification, prioritization, and remediation of the heap-based buffer overflow flaw in quickjs via the specified patch.

SI-16 Memory Protection partial match

prevent

Implements memory protection safeguards such as heap hardening and exploit mitigations to limit the impact of heap buffer overflow exploitation.

RA-5 Vulnerability Monitoring and Scanning partial match

detect

Enables vulnerability scanning to identify systems running vulnerable versions of quickjs-ng up to 0.11.0.

MITRE ATT&CK Enterprise TechniquesAI

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 →

Why these techniques?

Heap-based buffer overflow in QuickJS JavaScript engine exploitable remotely by unauthenticated attackers with no user interaction, directly enabling exploitation of public-facing applications.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

A vulnerability was determined in quickjs-ng quickjs up to 0.11.0. This vulnerability affects the function js_typed_array_constructor of the file quickjs.c. Executing a manipulation can lead to heap-based buffer overflow. The attack may be launched remotely. The exploit has been publicly…

disclosed and may be utilized. This patch is called c5d80831e51e48a83eab16ea867be87f091783c5. A patch should be applied to remediate this issue.

Deeper analysisAI

CVE-2026-0821 is a heap-based buffer overflow vulnerability in the quickjs-ng quickjs JavaScript engine, affecting versions up to 0.11.0. The issue resides in the js_typed_array_constructor function within the quickjs.c file and is associated with CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-122 (Heap-based Buffer Overflow). Published on 2026-01-10, it carries a CVSS v3.1 base score of 7.3 (High) with the vector AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.

The vulnerability can be exploited remotely by unauthenticated attackers with low attack complexity and no user interaction required. Manipulation of the affected function triggers the heap-based buffer overflow, potentially allowing limited impacts to confidentiality, integrity, and availability. An exploit has been publicly disclosed and may be utilized by attackers.

Mitigation requires applying the patch at commit c5d80831e51e48a83eab16ea867be87f091783c5 in the quickjs-ng/quickjs repository. Further details are available in GitHub issue #1296, including comment #3780003395, and pull request #1299.