CVE-2026-41331: OpenClaw DOS Vulnerability

CVE-2026-41331 Overview

CVE-2026-41331 is a resource consumption vulnerability affecting OpenClaw before version 2026.3.31. The vulnerability exists in the Telegram audio preflight transcription feature, where insufficient allowlist enforcement allows unauthorized group senders to trigger transcription processing. Attackers can exploit this flaw to initiate audio preflight operations before authorization checks are properly applied, leading to unauthorized resource or billing consumption.

Critical Impact

Unauthorized actors can trigger expensive audio transcription operations, potentially causing significant resource exhaustion and unexpected billing charges for affected OpenClaw deployments.

Affected Products

• OpenClaw versions prior to 2026.3.31
• OpenClaw Telegram integration module
• Telegram audio preflight transcription feature

Discovery Timeline

• 2026-04-21 - CVE-2026-41331 published to NVD
• 2026-04-21 - Last updated in NVD database

Technical Details for CVE-2026-41331

Vulnerability Analysis

This vulnerability is classified under CWE-408 (Incorrect Behavior Order: Early Amplification) and represents a resource consumption flaw in the Telegram integration module of OpenClaw. The core issue stems from the audio preflight transcription feature processing audio content before verifying whether the sender is authorized to trigger such operations.

When a Telegram message containing audio is received, the system initiates transcription processing without first validating the sender against the configured allowlist. This creates a window where unauthorized users can force the system to consume computational resources and potentially incur transcription service billing charges.

The vulnerability is exploitable over the network without requiring authentication, making it accessible to any user who can send messages to a Telegram group integrated with a vulnerable OpenClaw instance.

Root Cause

The root cause is improper behavior ordering where the audio preflight transcription operation executes before sender authorization checks are applied. The system fails to gate the transcription functionality on sender allowlist validation when access groups are configured, allowing unauthorized senders to bypass the intended access controls.

Attack Vector

The attack leverages the network-accessible Telegram bot integration. An attacker can:

1. Join or send messages to a Telegram group connected to a vulnerable OpenClaw instance
2. Send audio messages to the group
3. Trigger audio preflight transcription processing without being on the authorized sender allowlist
4. Repeatedly send audio content to cause sustained resource consumption or billing accumulation

The following patch addresses this vulnerability by adding sender authorization checks before audio preflight transcription:

   const disableAudioPreflight =
     (topicConfig?.disableAudioPreflight ??
       (groupConfig as TelegramGroupConfig | undefined)?.disableAudioPreflight) === true;
+  const senderAllowedForAudioPreflight =
+    !useAccessGroups || !allowForCommands.hasEntries || senderAllowedForCommands;
 
   let preflightTranscript: string | undefined;
   const needsPreflightTranscription =

Source: GitHub Commit Update

Detection Methods for CVE-2026-41331

Indicators of Compromise

• Unexpected spikes in audio transcription API calls or billing
• High volume of audio messages from unauthorized senders in monitored Telegram groups
• Unusual resource consumption patterns in OpenClaw processes related to transcription

Detection Strategies

• Monitor transcription service usage metrics for anomalous activity patterns
• Implement logging for all audio preflight transcription triggers with sender identification
• Set up alerts for transcription requests from senders not present in configured allowlists
• Review Telegram bot message logs for audio content from unexpected sources

Monitoring Recommendations

• Establish baseline metrics for normal transcription service usage
• Configure billing alerts to detect unexpected cost increases
• Implement rate limiting monitoring on audio processing endpoints
• Enable detailed audit logging for the Telegram integration module

How to Mitigate CVE-2026-41331

Immediate Actions Required

• Upgrade OpenClaw to version 2026.3.31 or later immediately
• Review current transcription service billing for signs of unauthorized usage
• Audit Telegram group configurations and sender allowlists
• Consider temporarily disabling audio preflight transcription until patched

Patch Information

The vulnerability has been addressed in OpenClaw version 2026.3.31. The fix introduces proper sender authorization validation before audio preflight transcription processing begins. The patch adds a senderAllowedForAudioPreflight check that ensures transcription only occurs for authorized senders when access groups are configured.

For patch details, see the GitHub Security Advisory and GitHub Commit Update.

Workarounds

• Disable audio preflight transcription by setting disableAudioPreflight: true in group or topic configuration until upgrade is possible
• Restrict Telegram group membership to trusted users only
• Implement external rate limiting on the Telegram bot integration
• Configure strict sender allowlists even for non-command functionality

# Configuration example - Disable audio preflight transcription as workaround
# In your OpenClaw Telegram group configuration:
# Set disableAudioPreflight to true to prevent unauthorized transcription

# Example environment configuration
OPENCLAW_TELEGRAM_DISABLE_AUDIO_PREFLIGHT=true

# Alternatively, configure in group settings JSON:
# {
#   "disableAudioPreflight": true
# }