# CVE-2026-56837: PraisonAI LinearBot missing webhook signature verification

Source: https://junglewise.ai/threats/cve-2026-56837-praisonai-linearbot-processes-unsigned-webhooks-when-linear  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-23. Updated: 2026-10-23  
License: CC BY 4.0 with a link back

CVE-2026-56837 · Severity: high · CVSS 8.6 · Published 2026-10-23

PraisonAI is a multi-agent system that integrates with Linear (a project management platform) via a webhook listener. When the LINEAR_WEBHOOK_SECRET environment variable is not set, the bot accepts unsigned webhook requests from any network caller, allowing attackers to forge events and trigger unauthorized agent execution. This can lead to model quota consumption, unauthorized API calls under the bot's identity, and injection of forged comments into Linear issues.

Technologies: [MervinPraison PraisonAI](https://junglewise.ai/threats/technologies/mervinpraison-praisonai), [praisonai (PyPI)](https://junglewise.ai/threats/technologies/pypi-praisonai). Vendors: [MervinPraison](https://junglewise.ai/threats/vendors/mervinpraison), [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-56837 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-56837 being exploited in the wild.

**How severe is CVE-2026-56837?** High severity, with a CVSS score of 8.6, published 23 October 2026.

**Which products and versions are affected?** MervinPraison PraisonAI 4.6.56 to 4.6.58; praisonai (PyPI) ECOSYSTEM:introduced=4.6.56,fixed=4.6.59.

**Is there a fix for CVE-2026-56837?** Yes. praisonai (PyPI): upgrade to 4.6.59 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-56837 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-56837?** Check whether you run MervinPraison PraisonAI or praisonai (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- praisonai (PyPI): upgrade to 4.6.59 or later

  ```sh
  pip install "praisonai>=4.6.59"
  ```


## Technical details

The vulnerability is an authentication bypass in PraisonAI's LinearBot webhook handler. When LINEAR_WEBHOOK_SECRET is absent or empty, the _handle_webhook() method skips HMAC-SHA256 signature verification entirely, accepting forged Linear-Event headers and webhookTimestamp values from any network caller. An unauthenticated attacker reaching the publicly exposed 0.0.0.0 listener can submit a crafted AgentSession event that is routed directly to the agent, allowing arbitrary agent invocation with attacker-controlled input.

## Affected products

- MervinPraison PraisonAI 4.6.56 to 4.6.58

## Identifiers

- CVE-2026-56837
- GHSA-fc26-m9pf-v56q
- PYSEC-2026-3510

## Timeline

- 2026-06-17: disclosed
- 2026-06-17: patched: version 4.6.59

## References

- [https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-fc26-m9pf-v56q](https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-fc26-m9pf-v56q)

## Related threats

- [PraisonAI authentication bypass in A2U event streaming](https://junglewise.ai/threats/cve-2026-57146-praisonai-a2u-incomplete-authentication-fix-leaves-current-serve)
- [PraisonAI sandbox escape when Landlock unavailable](https://junglewise.ai/threats/cve-2026-57144-praisonai-sandlocksandbox-falls-back-to-unrestricted-subprocess)
- [PraisonAI recipe policy bypass via YAML-approved tools](https://junglewise.ai/threats/cve-2026-57142-praisonai-recipe-workflow-policy-can-be-bypassed-by-declaring-and)
- [PraisonAI shell command injection in compute-bridged file tools](https://junglewise.ai/threats/cve-2026-57117-praisonai-compute-bridged-file-tools-allow-shell-command)
- [PraisonAI AgentOS authentication bypass in FastAPI deployment](https://junglewise.ai/threats/cve-2026-57116-praisonai-agentos-remains-unauthenticated-after-incomplete-fix)