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5 vulnerabilities by mtrudel
CVE-2026-39805 (GCVE-0-2026-39805)
Vulnerability from cvelistv5 – Published: 2026-05-01 20:34 – Updated: 2026-05-04 17:11
VLAI?
Title
CL.CL HTTP request smuggling via duplicate Content-Length in bandit
Summary
Inconsistent Interpretation of HTTP Requests vulnerability in mtrudel bandit allows HTTP request smuggling via duplicate Content-Length headers.
'Elixir.Bandit.Headers':get_content_length/1 in lib/bandit/headers.ex uses List.keyfind/3, which returns only the first matching header. When a request contains two Content-Length headers with different values, Bandit silently accepts it, uses the first value to read the body, and dispatches the remaining bytes as a second pipelined request on the same keep-alive connection. RFC 9112 §6.3 requires recipients to treat this as an unrecoverable framing error.
When Bandit sits behind a proxy that picks the last Content-Length value and forwards the request rather than rejecting it, an unauthenticated attacker can smuggle requests past edge WAF rules, path-based ACLs, rate limiting, and audit logging.
This issue affects bandit: before 1.11.0.
Severity ?
CWE
- CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Assigner
References
| URL | Tags | |
|---|---|---|
Impacted products
Credits
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CVE-2026-39804 (GCVE-0-2026-39804)
Vulnerability from cvelistv5 – Published: 2026-05-01 20:34 – Updated: 2026-05-04 17:11
VLAI?
Title
WebSocket permessage-deflate inflate has no output-size cap in bandit
Summary
Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion when WebSocket permessage-deflate compression is enabled.
'Elixir.Bandit.WebSocket.PerMessageDeflate':inflate/2 in lib/bandit/websocket/permessage_deflate.ex calls :zlib.inflate/2 with no output-size cap, then materializes the entire decompressed payload as a single binary via IO.iodata_to_binary/1. The websocket_options.max_frame_size option only bounds the on-the-wire (compressed) frame size, not the decompressed output. A high-ratio compressed frame (e.g. uniform data at ~1024:1 ratio) can stay well under any wire-size limit while forcing GiB-scale heap allocations in the connection process before any application code runs.
An unauthenticated attacker who can open a WebSocket connection can send a single such frame to exhaust the BEAM node's memory and trigger an OOM kill.
This vulnerability requires both Bandit's server-level websocket_options.compress and the per-upgrade compress: true option passed to WebSockAdapter.upgrade/4 to be enabled. Stock Phoenix and LiveView applications are not affected as they default to compress: false.
This issue affects bandit: from 0.5.9 before 1.11.0.
Severity ?
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
| URL | Tags | |
|---|---|---|
Impacted products
Credits
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CVE-2026-39807 (GCVE-0-2026-39807)
Vulnerability from cvelistv5 – Published: 2026-05-01 20:34 – Updated: 2026-05-04 17:11
VLAI?
Title
Client-supplied URI scheme trusted without transport verification in bandit
Summary
Reliance on Untrusted Inputs in a Security Decision vulnerability in mtrudel bandit allows unauthenticated transport-state spoofing on plaintext HTTP connections.
'Elixir.Bandit.Pipeline':determine_scheme/2 in lib/bandit/pipeline.ex returns the client-supplied URI scheme verbatim, ignoring the transport's secure? flag. HTTP/1.1 absolute-form request targets (e.g. GET https://victim/path HTTP/1.1) and the HTTP/2 :scheme pseudo-header are both attacker-controlled strings that flow through this function. Over a plaintext TCP connection, a client can declare https and Bandit will set conn.scheme = :https even though no TLS was negotiated.
Downstream Plug consumers that branch on conn.scheme are silently misled: Plug.SSL's already-secure branch skips its HTTP→HTTPS redirect, cookies emitted with secure: true are sent over plaintext, audit logs record requests as having arrived over HTTPS, and CSRF/SameSite gating may make incorrect decisions.
This issue affects bandit: from 1.0.0 before 1.11.0.
Severity ?
CWE
- CWE-807 - Reliance on Untrusted Inputs in a Security Decision
Assigner
References
| URL | Tags | |
|---|---|---|
Impacted products
Credits
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CVE-2026-42786 (GCVE-0-2026-42786)
Vulnerability from cvelistv5 – Published: 2026-05-01 20:34 – Updated: 2026-05-04 17:11
VLAI?
Title
WebSocket fragmented message reassembly unbounded in bandit
Summary
Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion.
The fragment reassembly path in 'Elixir.Bandit.WebSocket.Connection':handle_frame/3 in lib/bandit/websocket/connection.ex appends every incoming Continuation{fin: false} frame's payload to a per-connection iolist with no cumulative size cap. The existing max_frame_size option only bounds individual frames; a peer that streams an unbounded number of continuation frames without ever setting fin=1 grows BEAM heap linearly until the OS or a supervisor kills the process.
Because the accumulation happens before WebSock.handle_in/2 is called, the application has no opportunity to interpose a size check. Phoenix Channels and LiveView both run over WebSock on Bandit, so a stock Phoenix application exposes this surface as soon as it accepts socket connections.
This issue affects bandit: from 0.5.0 before 1.11.0.
Severity ?
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
| URL | Tags | |
|---|---|---|
Impacted products
Credits
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CVE-2026-42788 (GCVE-0-2026-42788)
Vulnerability from cvelistv5 – Published: 2026-05-01 20:34 – Updated: 2026-05-04 17:11
VLAI?
Title
HTTP/2 frame size limit checked after body is buffered in bandit
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.
Severity ?
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
| URL | Tags | |
|---|---|---|
Impacted products
Credits
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"credits": [
{
"lang": "en",
"type": "finder",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Mat Trudel"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
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"value": "Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated memory exhaustion via oversized HTTP/2 frames.\u003cp\u003e\u003ctt\u003e\u0027Elixir.Bandit.HTTP2.Frame\u0027:deserialize/2\u003c/tt\u003e in \u003ctt\u003elib/bandit/http2/frame.ex\u003c/tt\u003e checks the \u003ctt\u003eSETTINGS_MAX_FRAME_SIZE\u003c/tt\u003e limit only after pattern-matching \u003ctt\u003epayload::binary-size(length)\u003c/tt\u003e, 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 \u003ctt\u003emax_frame_size\u003c/tt\u003e negotiated during the HTTP/2 handshake (default 16 KiB per RFC 9113).\u003c/p\u003e\u003cp\u003eAn 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.\u003c/p\u003e\u003cp\u003eThis issue affects bandit: from 0.3.6 before 1.11.0.\u003c/p\u003e"
}
],
"value": "Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated memory exhaustion via oversized HTTP/2 frames.\n\n\u0027Elixir.Bandit.HTTP2.Frame\u0027: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).\n\nAn 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.\n\nThis issue affects bandit: from 0.3.6 before 1.11.0."
}
],
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"capecId": "CAPEC-130",
"descriptions": [
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"value": "CAPEC-130 Excessive Allocation"
}
]
}
],
"metrics": [
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"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 6.9,
"baseSeverity": "MEDIUM",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "LOW",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE"
},
"format": "CVSS",
"scenarios": [
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"value": "GENERAL"
}
]
}
],
"problemTypes": [
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"descriptions": [
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"cweId": "CWE-770",
"description": "CWE-770 Allocation of Resources Without Limits or Throttling",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-04T17:11:35.207Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
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"references": [
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"tags": [
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"related"
],
"url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-q6v9-r226-v65f"
},
{
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-42788.html"
},
{
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"url": "https://osv.dev/vulnerability/EEF-CVE-2026-42788"
},
{
"tags": [
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"url": "https://github.com/mtrudel/bandit/commit/1e8e55966da9129016b73d32f0e1df4630e3b463"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "HTTP/2 frame size limit checked after body is buffered in bandit",
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}
}
},
"cveMetadata": {
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"cveId": "CVE-2026-42788",
"datePublished": "2026-05-01T20:34:11.911Z",
"dateReserved": "2026-04-29T18:06:33.251Z",
"dateUpdated": "2026-05-04T17:11:35.207Z",
"state": "PUBLISHED"
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