LangBot: Missing webhook signature verification for Lark/Feishu events
Summary
LangBot through version 4.11.0 does not verify the signature of incoming Lark/Feishu webhook events. An unauthenticated attacker who knows a bot UUID can send forged message or card action events, which are processed by the LLM pipeline, tools and approval flows as if they came from other users. Exploitation requires an attacker to know the bot UUID and a reachable webhook endpoint; the CVSS 4.0 score of 8.3 is based on a high attack complexity.
Affected
- LangBot 0 to 4.11.0 (Lark/Feishu adapter, webhook mode)
- Both the lark-omni adapter and the legacy lark platform type are reported as affected
- Versions after 4.11.0: Unknown.
Fixed in
- Fixed version: Unknown.
- A fix (pull request #2628) adding X-Lark-Signature verification has been published, but its merge status and release were not confirmed.
Workaround
- Switch Lark/Feishu bots from webhook mode to the long-connection (WebSocket) mode, if supported.
- If webhook mode must remain, restrict the endpoint at the firewall or reverse proxy to Lark's published source addresses.
- Limit tool and approval permissions of Lark-connected bots.
- Do not treat the bot UUID as a secret.
Exploitation
- No evidence of exploitation in the wild found; not listed in KEV.
- CISA SSVC: Exploitation none, Automatable no, Technical Impact partial.
- No public proof of concept found; the issue #2627 describes the flaw in detail.
Our recommendation
- Check whether LangBot is running with Lark/Feishu in webhook mode and whether the endpoint is reachable from the internet.
- Switch to WebSocket mode or restrict the endpoint to Lark's source addresses until a verified fix is installed.
- Review tool and approval permissions of Lark-connected bots.
- Monitor LangBot logs for unexpected webhook requests and actions.
- Update to a release that contains the fix once the vendor confirms it.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE-2026-112265 on OpenCVE app.opencve.io
- VulnCheck advisory www.vulncheck.com
- LangBot issue #2627 github.com
- LangBot fix pull request #2628 github.com
- LangBot commit 43c481d github.com
- LangBot Lark wiki github.com
- VulDB entry 422377 vuldb.com
- LangBot v4.11.0 adapter.py github.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 13:34.
Original description (NVD)
LangBot through 4.11.0 contains a missing authenticity verification vulnerability that allows unauthenticated attackers to inject forged Lark/Feishu events by skipping signature checks. Attackers knowing a bot UUID can POST fabricated im.message.receive_v1 or card.action.trigger events to drive the LLM pipeline, tools, and approvals as other users.
NVD references (6)
- https://github.com/langbot-app/LangBot/blob/v4.11.0/src/langbot/pkg/api/http/controller/groups/webhooks.py
- https://github.com/langbot-app/LangBot/blob/v4.11.0/src/langbot/pkg/platform/adapters/lark/adapter.py
- https://github.com/langbot-app/LangBot/blob/v4.11.0/src/langbot/pkg/platform/sources/lark.py
- https://github.com/langbot-app/LangBot/commit/43c481d74a6388657b84baa7d292c613c75c24f9
- https://github.com/langbot-app/LangBot/issues/2627
- https://www.vulncheck.com/advisories/langbot-through-4.11.0-missing-lark-feishu-webhook-authenticity-verifica…
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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