TeleJSON < 6.0.0 DOM-based XSS via parse() Function

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

TeleJSON prior to 6.0.0 contains a DOM-based cross-site scripting vulnerability in the parse() function that allows attackers to execute arbitrary JavaScript by delivering a crafted JSON payload containing a malicious _constructor-name_ property value. The custom reviver passes the constructor name directly to new Function() without sanitization when recreating object prototypes, enabling attackers to inject arbitrary JavaScript through vectors such as postMessage in cross-frame communication contexts to achieve script execution within the application.

Source published

20 May 2026 18:00:44 UTC

Source modified

8 Nov 2026 14:04:01 UTC

Observed here

8 Nov 2026 16:11:25 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CVSS 3.1 · 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

TeleJSON prior to 6.0.0 contains a DOM-based cross-site scripting vulnerability in the parse() function that allows attackers to execute arbitrary JavaScript by delivering a crafted JSON payload containing a malicious _constructor-name_ property value. The custom reviver passes the constructor name directly to new Function() without sanitization when recreating object prototypes, enabling attackers to inject arbitrary JavaScript through vectors such as postMessage in cross-frame communication contexts to achieve script execution within the application.

Source published

May 20, 2026, 6:00:44 PM (timezone not stated)

Source modified

Nov 8, 2026, 2:04:01 PM (timezone not stated)

Observed here

9 Nov 2026 11:13:04 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

TeleJSON prior to 6.0.0 contains a DOM-based cross-site scripting vulnerability in the parse() function that allows attackers to execute arbitrary JavaScript by delivering a crafted JSON payload containing a malicious _constructor-name_ property value. The custom reviver passes the constructor name directly to new Function() without sanitization when recreating object prototypes, enabling attackers to inject arbitrary JavaScript through vectors such as postMessage in cross-frame communication contexts to achieve script execution within the application.

Source published

20 May 2026 20:16:41 UTC

Source modified

8 Oct 2026 16:17:16 UTC

Observed here

25 Oct 2026 12:17:20 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 2.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/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

CVSS 3.1 · [email protected] · Secondary · 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

## Summary telejson versions prior to 6.0.0 (released 2022) are vulnerable to DOM-based Cross-Site Scripting (XSS) through unsafe deserialisation. Attacker-controlled input from the `_constructor-name_` property in parsed JSON is passed directly to `new Function()` without sanitisation, allowing arbitrary JavaScript execution. ## Affected versions | Package | Affected | Fixed | |----------|-----------|----------| | telejson | < 6.0.0 | >= 6.0.0 | ## Details telejson's `parse()` function uses a custom reviver to reconstruct JavaScript objects from serialised JSON. When processing objects with a `_constructor-name_` property, the reviver passes the constructor name directly to `new Function()` to recreate the object's prototype. In versions prior to 6.0.0, this constructor name is not sanitised. An attacker who can deliver a crafted JSON payload to `telejson.parse()` (for example, via `postMessage` in applications that use telejson for cross-frame communication) can inject arbitrary JavaScript into the `new Function()` call. **Vulnerable code** ([`src/index.ts`, lines 293-299 at v5.3.3](https://github.com/storybookjs/telejson/blob/v5.3.3/src/index.ts#L293-L299)): ```ts if (isObject<ValueContainer>(value) && value['_constructor-name_']) { const name = value['_constructor-name_']; if (name !== 'Object') { const Fn = new Function(`return function ${name}(){}`)(); Object.setPrototypeOf(value, new Fn()); } ``` **Fixed code** ([`src/index.ts`, lines 340-346 at v6.0.0](https://github.com/storybookjs/telejson/blob/v6.0.0/src/index.ts#L340-L346)): ```ts if (isObject<ValueContainer>(value) && value['_constructor-name_'] && options.allowFunction) { const name = value['_constructor-name_']; if (name !== 'Object') { const Fn = new Function(`return function ${name.replace(/[\W_]+/g, '')}(){}`)(); Object.setPrototypeOf(value, new Fn()); } ``` The fix introduces two mitigations: a character allowlist via regex that strips non-word characters before they reach `new Function()`, and gating the entire code path behind the `allowFunction` option. ## Impact An attacker can execute arbitrary JavaScript in the context of the application using the vulnerable telejson version. Depending on the application, this could enable session hijacking, credential theft, or arbitrary DOM manipulation. ## Remediation Upgrade to telejson >= 6.0.0.

Source published

2 Apr 2026 23:21:23 UTC

Source modified

8 Jun 2026 20:30:58 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Publisher rating · LOW