HTTP/2 inbound flow control is not enforced in Bandit
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-770.
Summary
Bandit, an HTTP server for Elixir, from 0.3.1 before 1.14.0 does not enforce HTTP/2 inbound flow control. An unauthenticated remote attacker can request a response larger than the initial 65,535-byte window, withhold WINDOW_UPDATE, and then flood small DATA frames on that stream, because Bandit.HTTP2.Connection.handle_frame/3 forwards each frame without checking the receive window. The frames queue in the stream's mailbox until the BEAM node runs out of memory, which is CWE-770.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via DATA frames sent past the advertised receive window. The attacker requests a response larger than the 65,535-byte initial window and withholds WINDOW_UPDATE, so the stream process blocks while sending and stops reading, then floods small DATA frames on that stream. Every frame is queued in the stream's mailbox until the BEAM node runs out of memory. Bandit.HTTP2.Connection.handle_frame/3 in lib/bandit/http2/connection.ex forwards each DATA frame to the stream process without consulting the receive window, and Bandit.HTTP2.FlowControl.compute_recv_window/2 replenishes the window as data arrives rather than as it is consumed, and never answers a violation with FLOW_CONTROL_ERROR. This issue affects bandit: from 0.3.1 before 1.14.0.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
Upgrade bandit to version 1.14.0 or later, which fixes the issue.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA bandit (mtrudel) Fixed in 1.14.0
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
mtrudel bandit 1.14.0, 220b9dfd27f9a21305be2afc75cbe585ddc24e7a
11 records Highest priority Priority MEDIUM 10 MEDIUM, 1 LOW
Other records, highest priority first
- TI-2026-80361 Bandit frames still reach WebSock after server-initiated closePriority MEDIUM 61
- TI-2026-80382 HTTP/2 frames let clients hold Bandit request body reads openPriority MEDIUM 45
- TI-2026-80371 WebSocket 1-byte continuation frames exhaust memory in BanditPriority MEDIUM 45
Timeline
- 2026-10-26 Threatist record created from CVE-2026-108525
- 2026-10-26 CISA SSVC decision points changed
References
More mtrudel vulnerabilities
- TI-2026-81989 HTTP/2 request bodies made of 1-byte DATA frames amplify memory use in Bandit CVSS 4.0HIGH 8.7
- TI-2026-74311 Bandit HTTP/2 send timers reset, letting trickles pin stream processes CVSS 4.0HIGH 8.7
- TI-2026-52571 HTTP/2 connection-window starvation pins Plug processes indefinitely in Bandit CVSS 4.0HIGH 8.7
- TI-2026-46780 Quadratic CPU blow-up reassembling fragmented WebSocket messages in Bandit CVSS 4.0HIGH 8.7
- TI-2026-31007 WebSocket fragmented message reassembly unbounded in bandit CVSS 4.0HIGH 8.7
- TI-2026-28689 HTTP/1 chunked decoder infinite loop on requests with trailer fields in bandit CVSS 4.0HIGH 8.7
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences