CVE-2026-123561
Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion
Description
devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.
INFO
Published Date :
Nov. 8, 2026, 2:16 a.m.
Last Modified :
Nov. 8, 2026, 2:16 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | LOW | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | LOW | MITRE-CVE | ||||
| CVSS 3.1 | LOW | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update devalue to 5.9.3 or later.
- Ensure all input is properly sanitized.
- Review security configurations for bypasses.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-123561.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-123561 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-123561
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-123561 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-123561 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by [email protected]
Nov. 08, 2026
Action Type Old Value New Value Added Description devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/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 Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N Added CWE CWE-1321 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/123xxx/CVE-2026-123561.json">CVE-2026-123561</a> Added Reference https://github.com/sveltejs/devalue/security/advisories/GHSA-4q55-j62x-fr9h Added Reference https://www.vulncheck.com/advisories/sveltejs-devalue-before-5.9.3-proto-rejection-bypass-via-property-key-coercion