CVE-2026-109427

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.

CVSS v3 6.5 MEDIUM

6.5^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://gist.github.com/mansurmavlankulov/489554cad7b38e07b9651c217f00fffb
https://www.vulncheck.com/advisories/telegram-stremio-broken-object-authorization-via-stream-ids

Configurations

No configuration.

History

12 Oct 2026, 21:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-12 21:17

Updated : 2026-10-26 21:17

NVD link : CVE-2026-109427

Mitre link : CVE-2026-109427

CVE.ORG link : CVE-2026-109427

JSON object : View

Products Affected

No product.

CWE

CWE-639

Authorization Bypass Through User-Controlled Key

CWE-862

Missing Authorization

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