# CVE-2026-55891: PrivateBin reflected JSON injection in jsonld endpoints

Source: https://junglewise.ai/threats/cve-2026-55891-privatebin-reflected-json-injection-in-jsonld-endpoints  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-28. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-55891 · Severity: low · CVSS 3.1 · Published 2026-08-28

PrivateBin's JSON-LD API endpoints fail to properly escape user-supplied request URLs before inserting them into JSON responses. An attacker can craft a malicious request URL containing special characters (like quotes) that breaks out of the JSON structure, allowing injection of arbitrary key-value pairs into the response. The response is served with CORS headers and lacks MIME-type protection, potentially enabling structured-data consumers or other clients to misinterpret the injected content.

Technologies: [privatebin/privatebin (Packagist)](https://junglewise.ai/threats/technologies/privatebin-privatebin), [PrivateBin](https://junglewise.ai/threats/technologies/privatebin). Vendors: [Packagist](https://junglewise.ai/threats/vendors/packagist), [PrivateBin](https://junglewise.ai/threats/vendors/privatebin).

## Quick answers

**Is CVE-2026-55891 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55891 being exploited in the wild.

**How severe is CVE-2026-55891?** Low severity, with a CVSS score of 3.1, published 28 August 2026.

**Which products and versions are affected?** privatebin/privatebin (Packagist) <= 2.0.4, ECOSYSTEM:introduced=0,fixed=2.0.5; PrivateBin <= 2.0.4.

**Is there a fix for CVE-2026-55891?** Yes. privatebin/privatebin (Packagist): upgrade to 2.0.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55891 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-55891?** Check whether you run privatebin/privatebin (Packagist) or PrivateBin at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- privatebin/privatebin (Packagist): upgrade to 2.0.5 or later

  ```sh
  composer require privatebin/privatebin:^2.0.5
  ```


## Technical details

The vulnerability is an improper output encoding bug (CWE-116) in PrivateBin's JSON-LD endpoint handler. The root cause lies in the `Request::getRequestUri()` method, which uses PHP's `FILTER_SANITIZE_URL` filter—a function that does not strip quote characters (`"`, `'`), angle brackets (`<`, `>`), or other JSON-special characters. The unsanitized URI is then directly inserted into JSON-LD template files via `str_replace()` in `Controller::_jsonld()` without JSON-escaping, allowing an attacker to break out of a JSON string and inject arbitrary keys and values. For example, a request to `/?jsonld=types&x="injected":"pwned","y":"` would result in these quote characters being reflected unescaped into the response body. Additionally, the jsonld code path bypasses standard security headers (notably `X-Content-Type-Options: nosniff`), and the endpoint sets `Access-Control-Allow-Origin: *`, creating a defense-in-depth gap. No direct script execution has been demonstrated on modern browsers since JSON-LD is not HTML-sniffed, but the issue can be exploited by structured-data consumers or combined with other vulnerabilities. The fix requires proper JSON escaping of the URL before insertion and application of missing security headers.

## Affected products

- PrivateBin PrivateBin <= 2.0.4

## Identifiers

- CVE-2026-55891
- GHSA-xrjc-c68j-hp7w

## Timeline

- 2026-07-11: disclosed
- 2026-08-28: patched: Fixed in version 2.0.5

## References

- [https://api.github.com/users/iaohkut-from-NightWolf-Team](https://api.github.com/users/iaohkut-from-NightWolf-Team)
- [https://github.com/iaohkut-from-NightWolf-Team](https://github.com/iaohkut-from-NightWolf-Team)
- [https://api.github.com/users/iaohkut-from-NightWolf-Team/gists%7B/gist_id%7D](https://api.github.com/users/iaohkut-from-NightWolf-Team/gists%7B/gist_id%7D)
- [https://api.github.com/users/iaohkut-from-NightWolf-Team/repos](https://api.github.com/users/iaohkut-from-NightWolf-Team/repos)
- [https://avatars.githubusercontent.com/u/286391906?v=4](https://avatars.githubusercontent.com/u/286391906?v=4)
- [https://api.github.com/users/iaohkut-from-NightWolf-Team/events%7B/privacy%7D](https://api.github.com/users/iaohkut-from-NightWolf-Team/events%7B/privacy%7D)

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- [PrivateBin's template-switching feature allows arbitrary local file inclusion through path traversal](https://junglewise.ai/threats/cve-2025-64714-privatebin-s-template-switching-feature-allows-arbitrary-local)
- [PrivateBin vulnerable to malicious filename use for self-XSS / HTML injection locally for users](https://junglewise.ai/threats/cve-2025-64711-privatebin-vulnerable-to-malicious-filename-use-for-self-xss-html)
- [PrivateBin is missing HTML sanitization of attached filename in file size hint](https://junglewise.ai/threats/cve-2025-62796-privatebin-is-missing-html-sanitization-of-attached-filename-in)
- [PrivateBin allows shortening of URLs for other domains](https://junglewise.ai/threats/cve-2024-39899-privatebin-allows-shortening-of-urls-for-other-domains)