Claude-generated Linear webhook code skipped signature checks when the secret was unset, letting unauthenticated callers trigger agents and post comments.

How AI contributed: Direct introductionPublished Jun 18, 2026 in mervinpraison/praisonaiAll 19 findings in this repository

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LinearBot webhook signature fail-open: LinearBot in src/praisonai/praisonai/bots/linear.py started a public webhook listener on 0.0.0.0 and silently skipped Linear-Signature HMAC verification when LINEAR_WEBHOOK_SECRET was unset, allowing unauthenticated network callers to forge AgentSession webhooks and trigger arbitrary agent executions and Linear comment posting.

Root cause

Injection & unsafe execution introduced

feat: add Linear integration — agentic control plane with tools + LinearBot + AgentSession webhooks

AI-assisted change: Claude

ed89d20bcb

src/praisonai/praisonai/bots/linear.py

Fix

Security fix

refactor: harden input validation and access controls

AI-assisted fix: Cursor · MervinPraison

2adfe7e832

src/praisonai/praisonai/bots/linear.py

Case facts

CVE ID: CVE-2026-56837
GHSA ID: GHSA-FC26-M9PF-V56Q
Published: Jun 18, 2026
Severity: Not scored
Language: Python
AI tool: Claude
AI role: Direct introduction
Vulnerable release: >= 4.6.56, <= 4.6.58
Fixed release: 4.6.59

Advisory source

AI-assisted change

AI-assisted changesrc/praisonai/praisonai/bots/linear.py source mervinpraison/praisonai@ed89d20bcb+89−0

@@ -0,0 +1,512 @@+"""+Linear Bot implementation for PraisonAI.+

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+Supports Linear agent integration via AgentSession webhooks.++Usage:+    bot = LinearBot(token="linear-oauth-token", agent=agent, +                   signing_secret="webhook-secret")+    await bot.start()+"""++from __future__ import annotations++import asyncio+import hashlib+import hmac+import json+import logging+import os+import time+from typing import Any, Callable, Dict, List, Optional, TYPE_CHECKING, Union++if TYPE_CHECKING:+    from praisonaiagents import Agent++from praisonai.bots._protocol_mixin import ChatCommandMixin, MessageHookMixin+from praisonaiagents.bots import (+    BotConfig,+    BotMessage,+    BotUser,+    BotChannel,+    MessageType,+)++from ._commands import format_status, format_help+from ._session import BotSessionManager+from ._rate_limit import RateLimiter+from ._ack import AckReactor++logger = logging.getLogger(__name__)++# Linear GraphQL endpoint+LINEAR_API_BASE = "https://api.linear.app/graphql"+++class LinearBot(ChatCommandMixin, MessageHookMixin):+    """Linear bot runtime for PraisonAI agents.++    Connects an agent to Linear via AgentSession webhooks, handling+    mentions, assignments, and providing full bot functionality.++    Example:+        from praisonai.bots import LinearBot+        from praisonaiagents import Agent++        agent = Agent(name="assistant")+        bot = LinearBot(+            token="YOUR_OAUTH_TOKEN",+            signing_secret="YOUR_WEBHOOK_SECRET",+            agent=agent,+        )++        await bot.start()+    """++    def __init__(+        self,+        token: str = "",+        agent: Optional["Agent"] = None,+        config: Optional[BotConfig] = None,+        signing_secret: str = "",+        webhook_port: int = 8080,+        webhook_path: str = "/webhook",+        **kwargs,+    ):+        # Store extra kwargs for forward compatibility+        self._extra_kwargs = kwargs+

+        self._token = token or os.environ.get("LINEAR_OAUTH_TOKEN", "") or os.environ.get("LINEAR_API_KEY", "")+        self._agent = agent+        self.config = config or BotConfig(token=self._token, mode="webhook")+        self._signing_secret = signing_secret or os.environ.get("LINEAR_WEBHOOK_SECRET", "")+        self._webhook_port = webhook_port+        self._webhook_path = webhook_path+

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+        self._is_running = False+        self._started_at: Optional[float] = None+        self._bot_user: Optional[BotUser] = None+

The new LinearBot accepts an optional signing_secret (or LINEAR_WEBHOOK_SECRET env) and defaults it to empty, so a freshly started bot has no HMAC key configured by default.

Security fix

Fixsrc/praisonai/praisonai/bots/linear.py source mervinpraison/praisonai@2adfe7e832+5−1

@@ -240,12 +240,16 @@ async def _handle_webhook(self, request) -> Any:             # Read raw body for signature verification             raw_body = await request.read()             -            # Verify signature if secret is configured+            from praisonai.bots.webhook_security import webhooks_require_verification+             if self._signing_secret:                 signature = request.headers.get("Linear-Signature", "")                 if not self._verify_signature(raw_body, signature):                     logger.warning("Invalid webhook signature")                     return web.Response(status=401, text="Invalid signature")+            elif webhooks_require_verification():+                logger.warning("Webhook rejected: signing secret not configured")+                return web.Response(status=401, text="Webhook verification not configured")                          # Parse JSON body             try:

The webhook handler only verifies the Linear-Signature when a secret is set; with the secret absent, the request is processed without any signature check, letting unauthenticated network callers drive the bot.

Patch fingerprints

AI-assisted change f4d5ba77a21b919b343f2a3596739aebf834313f1fa65ce83d8d377d13ddaadf · Fix ad79593fa8a84fbb37aaa3592c21985552bdb47e174da6d6641496d48465b9f0

Claude-generated Linear webhook code skipped signature checks when the secret was unset, letting unauthenticated callers trigger agents and post comments.

Show full advisory description

AI-assisted change

AI-assisted changesrc/praisonai/praisonai/bots/linear.py source mervinpraison/praisonai@ed89d20bcb+89−0

@@ -0,0 +1,512 @@+"""+Linear Bot implementation for PraisonAI.+

Show 75 hidden lines

+Supports Linear agent integration via AgentSession webhooks.++Usage:+    bot = LinearBot(token="linear-oauth-token", agent=agent, +                   signing_secret="webhook-secret")+    await bot.start()+"""++from __future__ import annotations++import asyncio+import hashlib+import hmac+import json+import logging+import os+import time+from typing import Any, Callable, Dict, List, Optional, TYPE_CHECKING, Union++if TYPE_CHECKING:+    from praisonaiagents import Agent++from praisonai.bots._protocol_mixin import ChatCommandMixin, MessageHookMixin+from praisonaiagents.bots import (+    BotConfig,+    BotMessage,+    BotUser,+    BotChannel,+    MessageType,+)++from ._commands import format_status, format_help+from ._session import BotSessionManager+from ._rate_limit import RateLimiter+from ._ack import AckReactor++logger = logging.getLogger(__name__)++# Linear GraphQL endpoint+LINEAR_API_BASE = "https://api.linear.app/graphql"+++class LinearBot(ChatCommandMixin, MessageHookMixin):+    """Linear bot runtime for PraisonAI agents.++    Connects an agent to Linear via AgentSession webhooks, handling+    mentions, assignments, and providing full bot functionality.++    Example:+        from praisonai.bots import LinearBot+        from praisonaiagents import Agent++        agent = Agent(name="assistant")+        bot = LinearBot(+            token="YOUR_OAUTH_TOKEN",+            signing_secret="YOUR_WEBHOOK_SECRET",+            agent=agent,+        )++        await bot.start()+    """++    def __init__(+        self,+        token: str = "",+        agent: Optional["Agent"] = None,+        config: Optional[BotConfig] = None,+        signing_secret: str = "",+        webhook_port: int = 8080,+        webhook_path: str = "/webhook",+        **kwargs,+    ):+        # Store extra kwargs for forward compatibility+        self._extra_kwargs = kwargs+

+        self._token = token or os.environ.get("LINEAR_OAUTH_TOKEN", "") or os.environ.get("LINEAR_API_KEY", "")+        self._agent = agent+        self.config = config or BotConfig(token=self._token, mode="webhook")+        self._signing_secret = signing_secret or os.environ.get("LINEAR_WEBHOOK_SECRET", "")+        self._webhook_port = webhook_port+        self._webhook_path = webhook_path+

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+        self._is_running = False+        self._started_at: Optional[float] = None+        self._bot_user: Optional[BotUser] = None+

The new LinearBot accepts an optional signing_secret (or LINEAR_WEBHOOK_SECRET env) and defaults it to empty, so a freshly started bot has no HMAC key configured by default.

Security fix

Fixsrc/praisonai/praisonai/bots/linear.py source mervinpraison/praisonai@2adfe7e832+5−1

@@ -240,12 +240,16 @@ async def _handle_webhook(self, request) -> Any:             # Read raw body for signature verification             raw_body = await request.read()             -            # Verify signature if secret is configured+            from praisonai.bots.webhook_security import webhooks_require_verification+             if self._signing_secret:                 signature = request.headers.get("Linear-Signature", "")                 if not self._verify_signature(raw_body, signature):                     logger.warning("Invalid webhook signature")                     return web.Response(status=401, text="Invalid signature")+            elif webhooks_require_verification():+                logger.warning("Webhook rejected: signing secret not configured")+                return web.Response(status=401, text="Webhook verification not configured")                          # Parse JSON body             try: