HTTP/2 frame size limit checked after body is buffered 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 · Low
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-770.
Summary
Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated memory exhaustion via oversized HTTP/2 frames. 'Elixir.Bandit.HTTP2.Frame':deserialize/2 in lib/bandit/http2/frame.ex checks the SETTINGS_MAX_FRAME_SIZE limit only after pattern-matching payload::binary-size(length), which requires the entire frame body to be present in memory before either the accept or reject clause can fire. A peer that announces a frame length up to the 24-bit maximum (~16 MiB) causes the server to buffer that entire body before the size guard is evaluated, regardless of the max_frame_size negotiated during the HTTP/2 handshake (default 16 KiB per RFC 9113). An unauthenticated attacker holding many concurrent connections can force the server to buffer far more memory than the negotiated frame size limit should permit, leading to memory pressure and potential denial of service. This issue affects bandit: from 0.3.6 before 1.11.0.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- 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
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| mtrudel | bandit | 0.3.6 to before 1.11.0 | 1.11.0 | Patch available | CNA |
| — | bandit (Hex) | 0.3.5 to before 1.11.0 | 1.11.0 | Patch available | GHSA-q6v9-r226-v65f |
- bandit Vendormtrudel Affected 0.3.6 to before 1.11.0 Fixed in 1.11.0 Patch available CNA
- bandit (Hex) Vendor— Affected 0.3.5 to before 1.11.0 Fixed in 1.11.0 Patch available GHSA-q6v9-r226-v65f
Remediation
- Fix · CNA bandit (mtrudel) Fixed in 1.11.0
- Fix · GHSA-q6v9-r226-v65f bandit (Hex) Fixed in 1.11.0 Advisory →
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
mtrudel bandit 1.11.0
5 records Highest priority Priority HIGH 5 HIGH
Other records, highest priority first
- TI-2026-31007 WebSocket fragmented message reassembly unbounded in banditPriority HIGH 77
- TI-2026-28687 WebSocket permessage-deflate inflate has no output-size cap in banditPriority HIGH 75
- TI-2026-28690 Client-supplied URI scheme trusted without transport verification in banditPriority HIGH 67
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2026-42788
- 2026-10-03 Alias added: GHSA-q6v9-r226-v65f
References
Advisory 2
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
- CVE-2026-42788 · CVE Program
- CVE-2026-42788 · NVD
- FIRST EPSS
- GHSA-q6v9-r226-v65f · GitHub Advisory Database · CC BY 4.0
- CVE-2026-42788 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences