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 4.0
- 7.1
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 3.1
- 6.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - EPSS
- 0.2% chance of exploitation in the next 30 days; higher than 10% of CVEs (scores of 2026-10-25)
- CWEs
- CWE-639, CWE-862
- Published
- Modified
- Record from
- the NVD, synced