Security readout for executives and security teams
Plain-English summary
CVE-2026-0821 is a heap-based buffer overflow in quickjs-ng quickjs through 0.11.0. It affects JavaScript typed array construction and may be triggered remotely where untrusted JavaScript reaches an affected runtime. Public exploit information is reported, but CISA KEV listing is not indicated in the provided sources.
Executive priority
Treat as a priority fix for any externally reachable or customer-facing use of quickjs-ng. Public exploit disclosure raises urgency, but business impact depends on whether untrusted JavaScript can reach the affected component.
Technical view
The flaw is in js_typed_array_constructor in quickjs.c. Manipulated input can cause a heap-based buffer overflow, mapped to CWE-119 and CWE-122. VulDB rates it high with CVSS 2.0 score 7.5. A fixing commit is identified as c5d80831e51e48a83eab16ea867be87f091783c5.
Likely exposure
Organizations are exposed if they embed or ship quickjs-ng quickjs versions 0.1 through 0.11.0, especially in services, products, or tools that execute attacker-controlled JavaScript. Direct internet exposure depends on how the runtime is integrated.
Exploitation context
The source bundle says the attack may be launched remotely and that exploit details have been publicly disclosed. No KEV listing is provided, so active exploitation should not be assumed from these sources alone.
Researcher notes
Evidence comes from CVE/VulDB metadata and linked GitHub issue, pull request, and commit. The provided data names the vulnerable function and patch commit but does not establish observed in-the-wild exploitation or downstream product impact.
Mitigation direction
- Identify products and services embedding quickjs-ng quickjs.
- Upgrade or apply the vendor patch commit c5d80831e51e48a83eab16ea867be87f091783c5.
- Restrict untrusted JavaScript execution until remediation is verified.
- Monitor the GitHub issue, pull request, and CVE record for updated vendor guidance.
Validation and detection
- Inventory quickjs-ng quickjs versions across source, binaries, containers, and dependencies.
- Confirm affected versions 0.1 through 0.11.0 are not present.
- Verify the fixing commit or an equivalent vendor release is included.
- Review exposed workflows that process untrusted JavaScript input.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-119: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-122: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-0821 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (2.0)
- Known Exploited
- No
- Published
Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P/E:POC/RL:OF/RC:C
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
AV:N/AC:L/Au:N/C:P/I:P/A:P/E:POC/RL:OF/RC:C106.4Primary CVE scoreVulnerability scoring details
Base CVSS 2.0 score
7.5HighVector: AV:N/AC:L/Au:N/C:P/I:P/A:P/E:POC/RL:OF/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- VDB-340355 | quickjs-ng quickjs quickjs.c js_typed_array_constructor heap-based overflowCVE reference · vdb-entry, technical-description
- VDB-340355 | CTI Indicators (IOB, IOC, IOA)CVE reference · signature, permissions-required
- Submit #731780 | quickjs-ng quickjs v0.11.0 Heap-based Buffer OverflowCVE reference · third-party-advisory
- https://github.com/quickjs-ng/quickjs/issues/1296CVE reference · issue-tracking, exploit
- https://github.com/quickjs-ng/quickjs/pull/1299CVE reference · issue-tracking
- https://github.com/quickjs-ng/quickjs/commit/c5d80831e51e48a83eab16ea867be87f091783c5CVE reference · patch
- https://github.com/quickjs-ng/quickjs/CVE reference · product
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Restriction of Operations within the Bounds of a Memory Buffer
Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Heap-based Buffer Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.