TeleJSON: DOM XSS via unsanitised constructor name in new Function()

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

2.1 · 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 · score source

EPSS

• CVE-2026-47099: 0.36% estimated exploitation activity in the next 30 days; percentile 29.57 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

2 Apr 2026, 23:21 UTC

Last modified by the source

8 Jun 2026, 20:30 UTC

Source last checked

26 Oct 2026, 12:53 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-ccgf-5rwj-j3hv

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-ccgf-5rwj-j3hv

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# Patch Next advisory brief: CVE-2026-47099

Advisory: TeleJSON: DOM XSS via unsanitised constructor name in `new Function()`
IDs: CVE-2026-47099, GHSA-ccgf-5rwj-j3hv
Record: https://patchnext.com/advisories/cve-2026-47099 (revision 3, source checked 26 Oct 2026, 12:53 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: telejson 6.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm telejson: affected < 6.0.0; fixed in 6.0.0

## Suggested inspection (read-only)
- `npm ls telejson --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on telejson.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-ccgf-5rwj-j3hv (OSV record GHSA-ccgf-5rwj-j3hv lists affected ranges: npm telejson >=0 <6.0.0 (fixed))
- Verified: https://github.com/advisories/GHSA-ccgf-5rwj-j3hv (GitHub-reviewed advisory GHSA-ccgf-5rwj-j3hv lists affected ranges: npm telejson >=0 <6.0.0)

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