Bandit chunked request bodies of 1-byte chunks amplify memory use
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 is affected from 0.1.0 before 1.14.0. Its HTTP/1.1 chunked body reader keeps each chunk as a separate term and does not limit the number of chunks, so a request body of many 1-byte chunks uses far more memory and CPU than its data size. An unauthenticated remote attacker can exhaust server memory and CPU by sending such a request body (CWE-770). The reader also drains unread bodies on keep-alive connections, so a route does not need to read the body to be exposed.
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/1.1 chunked body reader of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory and CPU via a request body made of many 1-byte chunks. The chunked reader in lib/bandit/http1/socket.ex keeps every chunk as its own list cell and binary term until IO.iodata_to_binary/1 joins them, and nothing limits the number of chunks. The :length option of read_body/2 counts only data bytes, so tiny chunks cost far more memory than their payload: 48 MB of 1-byte chunks grew one handler process to about 500 MB and took about 6 s of CPU. The route does not need to read the body, because on keep-alive connections ensure_completed/1 drains unread bodies through the same reader. This issue affects bandit: from 0.1.0 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.
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-2026-111101
- 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