---
id: CVE-2026-109427
title: >-
  Telegram-Stremio through 5.1.0 contains a broken object-level authorization
  vulnerability that allows authenticated token holders to access arbitrary chat
  messages by forging unsigned, unauthenticated stream IDs decoded via
  encode_string…
summary: >-
  Telegram-Stremio through 5.1.0 contains a broken object-level authorization
  vulnerability that allows authenticated token holders to access arbitrary chat
  messages by forging unsigned, unauthenticated stream IDs decoded via
  encode_string…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-639
  - CWE-862
published: '2026-10-12'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T21:17:11.460'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109427'
references:
  - url: 'https://gist.github.com/mansurmavlankulov/489554cad7b38e07b9651c217f00fffb'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/telegram-stremio-broken-object-authorization-via-stream-ids
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-12T22:05:40.356Z'
---

## Overview

Telegram-Stremio through 5.1.0 contains a broken object-level authorization vulnerability that allows authenticated token holders to access arbitrary chat messages by forging unsigned, unauthenticated stream IDs decoded via encode_string/decode_string functions. Attackers can craft or enumerate sequential msg_id values and set a global flag in the stream_handler endpoint to route requests through the operator's personal Userbot account, exposing private channels, groups, and Saved Messages, while the unauthenticated thumb_handler endpoint further discloses thumbnails from those same chats without any token validation.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.