What’s Vulnerable › Vulnerabilities

CVE-2026-109427: Telegram-Stremio 5.1.0 Broken Object Authorization via Stream IDs

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-12 · updated 2026-10-26
• Weakness: CWE-639

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.

Affected products

• weebzone Telegram-Stremio: through 5.1.0

References

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

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