Cyber Resilience

CVE-2026-30226

Svelte Devalue ≤ 5.6.4

Published
11 March 2026
Modified
17 March 2026
Patch / advisory
View advisory
CVSS Score v4 6.3
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/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 30th percentile
Risk Priority 31 floored blend · peak EPSS

Summary

CVE-2026-30226 is a medium-severity Prototype Pollution (CWE-1321) vulnerability in Svelte Devalue. Its CVSS base score is 6.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 30th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

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-2026-30226 is a prototype pollution vulnerability affecting the Svelte devalue JavaScript library, which serializes values into strings when JSON.stringify is insufficient. Versions 5.6.3 and earlier are vulnerable in the devalue.parse and devalue.unflatten functions, which can be exploited through maliciously crafted payloads. The issue is classified under CWE-1321 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), highlighting high availability impact.

Remote attackers require no privileges or user interaction to exploit this vulnerability over the network with low complexity. By supplying crafted payloads to the affected functions, attackers can pollute the Object prototype, potentially leading to denial of service (DoS) conditions or type confusion in applications that process untrusted input through devalue.

The vulnerability is fixed in devalue version 5.6.4. Security practitioners should upgrade to this version or later. Additional details are available in the GitHub Security Advisory at https://github.com/sveltejs/devalue/security/advisories/GHSA-cfw5-2vxh-hr84.

EU & UK References

Vulnerability Data

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. In devalue v5.6.3 and earlier, devalue.parse and devalue.unflatten were susceptible to prototype pollution via maliciously crafted payloads. Successful exploitation could lead to…

more

Denial of Service (DoS) or type confusion. This vulnerability is fixed in 5.6.4.

CWE(s)
CWE-1321

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.
attack.mitre.org →
T1059 Command and Scripting Interpreter Execution
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1565 Data Manipulation Impact
Adversaries may insert, delete, or manipulate data in order to influence external outcomes or hide activity, thus threatening the integrity of the data.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-22774Same product: Svelte Devalue
CVE-2026-22775Same product: Svelte Devalue
CVE-2026-42570Same product: Svelte Devalue
CVE-2024-36578Shared CWE-1321
CVE-2026-34621Shared CWE-1321
CVE-2025-3193Shared CWE-1321
CVE-2024-30564Shared CWE-1321
CVE-2024-39008Shared CWE-1321
CVE-2026-44966Shared CWE-1321
CVE-2026-59206Shared CWE-1321

Affected Assets

svelte
devalue
≤ 5.6.4

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)
  • V15.3.6

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 input validation and safe property assignment to prevent prototype pollution.

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.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development catches prototype-pollution flaws before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and object-handling controls that directly prevent prototype pollution.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for safeguards against unsafe object attribute manipulation.

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

Secure architecture principles reduce the likelihood of prototype pollution through safe design patterns.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prohibit unsafe prototype attribute assignment and require defensive checks.

A.8.32 Change management partial match
prevents

Change-management processes ensure security fixes for prototype-pollution issues are tracked and deployed.

References