## Vulnerability

The ACP bridge accepted very large prompt text blocks and could assemble oversized prompt payloads before forwarding them to `chat.send`.

Because ACP runs over local stdio, this mainly affects local ACP clients (for example IDE integrations) that send unusually large inputs.

## Affected Packages / Versions

- Package: `openclaw` (npm)
- Affected versions: `<= 2026.2.17`
- Patched version: `2026.2.18` (planned next release)

## Impact

- Local ACP sessions may become less responsive when very large prompts are submitted
- Larger-than-expected model usage/cost when oversized text is forwarded
- No privilege escalation and no direct remote attack path in the default ACP model

## Affected Components

- `src/acp/event-mapper.ts`
- `src/acp/translator.ts`

## Remediation

- Enforce a 2 MiB prompt-text limit before concatenation
- Count inter-block newline separator bytes during pre-concatenation size checks
- Keep final outbound message-size validation before `chat.send`
- Avoid stale active-run session state when oversized prompts are rejected
- Add regression tests for oversize rejection and active-run cleanup

## Fix Commit(s)

- `732e53151e8fbdfc0501182ddb0e900878bdc1e3`
- `ebcf19746f5c500a41817e03abecadea8655654a`
- `63e39d7f57ac4ad4a5e38d17e7394ae7c4dd0b9c`

Thanks @aether-ai-agent for reporting.

CWE-400 Uncontrolled Resource Consumption