CVE-2026-109427
HIGH
MEDIUM
Priority: 0.01
BB Relevance:
64/100
Published: 2026-10-12
Modified: 2026-10-26
First seen: 2026-10-29
Status: active
Attack Surface
Network
Low Complexity
No Interaction
Conf. Impact
CVSS Vector Breakdown
AV:
Network
AC:
Low
PR:
Low
UI:
None
AT:
None
VC:
High
VI:
None
VA:
None
Description
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.