GHSA-j944-w549-3453

Source

https://github.com/advisories/GHSA-j944-w549-3453

Import Source

https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-j944-w549-3453/GHSA-j944-w549-3453.json

JSON Data

https://api.osv.dev/v1/vulns/GHSA-j944-w549-3453

Aliases

CVE-2026-42553

Published

2026-05-07T16:40:52Z

Modified

2026-06-09T00:00:19Z

Severity

7.1 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N CVSS Calculator

Summary

Cinny vulnerable to access token disclosure via invalidated emoji pack avatar URL in service worker

Details

Impact

A remote authenticated attacker who shares a room with a victim and has permissions to create room emotes (for example in a DM) can cause the victim's client to send their Matrix access token to an attacker-controlled server. This occurs when the victim opens the emoji or sticker picker for the room containing a malicious emote pack.

The root causes are:

(1) an incorrect fallback in EmojiBoard that uses untrusted pack.meta.avatar (user-controlled) without converting/validating it as an MXC URL, allowing arbitrary HTTP(S) URLs to be used; and

(2) the service worker attaching the user's Authorization bearer token to all outbound GET requests whose URL contains /_matrix/client/v1/media/download or /_matrix/client/v1/media/thumbnail without verifying the request host matches the configured homeserver origin. An attacker-controlled URL containing those path fragments and permissive CORS will receive the victim's Authorization header (access token).

Impacted users: anybody using affected Cinny web app versions who opens the emoji/sticker picker in a room containing a malicious emote pack and who is logged in (authenticated).

Patches

Version with fixes: https://github.com/cinnyapp/cinny/releases/tag/v4.10.3

Database specific

{
    "cwe_ids": [
        "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-07T16:40:52Z",
    "nvd_published_at": "2026-05-27T18:16:22Z",
    "severity": "HIGH"
}

References

Affected packages

npm / cinny

Package

Name: cinny; View open source insights on deps.dev
Purl: pkg:npm/cinny

Affected ranges

Type: SEMVER
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Fixed

4.10.3

Database specific

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-j944-w549-3453/GHSA-j944-w549-3453.json"