Allocation of Resources Without Limits or Throttling Affecting bandit package, versions >=0.5.1 <1.11.0
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-HEX-BANDIT-16346345
- published3 May 2026
- disclosed1 May 2026
- creditPJUllrich
Introduced: 1 May 2026
NewCVE-2026-42786 (opens in a new tab)How to fix?
Upgrade bandit to version 1.11.0 or higher.
Overview
bandit is a HTTP server for Plug and WebSock apps.
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling via the Bandit.WebSocket.Connection fragmented-frame handling in the WebSocket components. An attacker can force the server to buffer unbounded fragmented messages or trigger protocol errors by sending a long sequence of continuation frames, including zero-length non-final continuations. The vulnerable path accepts fragmented WebSocket payloads without enforcing a message-size limit across continuation frames, so a client can stream arbitrarily large messages and consume memory until the connection or process is disrupted. It also accepts empty non-final continuation frames, allowing a peer to drive the connection into malformed fragmentation states that terminate the WebSocket session and disrupt service for connected users.
Workarounds
- Set
max_fragmented_message_sizeon Bandit’s WebSocket options to a finite value to cap the total size of a fragmented message and prevent a single client from buffering unbounded continuation frames into memory. - Keep
max_frame_sizeenabled with a nonzero limit to bound the size of each individual WebSocket frame and reduce the amount of data any one frame can contribute to a fragmented-message flood.