CVE-2026-114213 (GCVE-0-2026-114213)
Vulnerability from cvelistv5 – Published: 2026-10-26 13:30 – Updated: 2026-10-26 15:35
VLAI
EPSS
VEX
Title
WebSocket 1-byte continuation frames bypass `max_fragmented_message_size` in Bandit
Summary
Allocation of Resources Without Limits or Throttling vulnerability in the WebSocket fragment reassembly of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a fragmented message made of many 1-byte continuation frames.
Bandit.WebSocket.Connection checks max_fragmented_message_size against the payload bytes received, but keeps every non-final continuation frame as a new list cell around its own binary, and nothing limits the number of fragments. A 1-byte fragment costs 7 bytes on the wire but about 150 to 170 bytes of server memory, so one connection can hold about 150 times the configured limit, roughly 1.2 to 1.4 GB at the default 8 MB. Ping frames between fragments keep the connection alive past the idle timeout.
This issue affects bandit: from 1.11.0 before 1.14.0.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-26 15:03 UTC
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://github.com/mtrudel/bandit/security/adviso… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-114213.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-114213 | related |
| https://github.com/mtrudel/bandit/commit/21612c7c… | related |
| https://github.com/mtrudel/bandit/commit/220b9dfd… | patch |
Impacted products
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"dateUpdated": "2026-10-26T15:32:57.015Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"packageName": "bandit",
"packageURL": "pkg:hex/bandit",
"product": "bandit",
"repo": "https://github.com/mtrudel/bandit",
"vendor": "mtrudel",
"versions": [
{
"lessThan": "1.14.0",
"status": "affected",
"version": "1.11.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"packageName": "mtrudel/bandit",
"packageURL": "pkg:github/mtrudel/bandit",
"product": "bandit",
"repo": "https://github.com/mtrudel/bandit",
"vendor": "mtrudel",
"versions": [
{
"lessThan": "220b9dfd27f9a21305be2afc75cbe585ddc24e7a",
"status": "affected",
"version": "21612c7c7b1ce43eccd36d3af3a2299d23513667",
"versionType": "git"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.14.0",
"versionStartIncluding": "1.11.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "reporter",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Mat Trudel"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen / EEF"
}
],
"dateAssigned": "2026-10-23T12:53:37.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAllocation of Resources Without Limits or Throttling vulnerability in the WebSocket fragment reassembly of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a fragmented message made of many 1-byte continuation frames.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eBandit.WebSocket.Connection\u003c/code\u003e checks \u003ccode\u003emax_fragmented_message_size\u003c/code\u003e against the payload bytes received, but keeps every non-final continuation frame as a new list cell around its own binary, and nothing limits the number of fragments. A 1-byte fragment costs 7 bytes on the wire but about 150 to 170 bytes of server memory, so one connection can hold about 150 times the configured limit, roughly 1.2 to 1.4 GB at the default 8 MB. Ping frames between fragments keep the connection alive past the idle timeout.\u003c/p\u003e\n\u003cp\u003eThis issue affects bandit: from 1.11.0 before 1.14.0.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Allocation of Resources Without Limits or Throttling vulnerability in the WebSocket fragment reassembly of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a fragmented message made of many 1-byte continuation frames.\n\n`Bandit.WebSocket.Connection` checks `max_fragmented_message_size` against the payload bytes received, but keeps every non-final continuation frame as a new list cell around its own binary, and nothing limits the number of fragments. A 1-byte fragment costs 7 bytes on the wire but about 150 to 170 bytes of server memory, so one connection can hold about 150 times the configured limit, roughly 1.2 to 1.4 GB at the default 8 MB. Ping frames between fragments keep the connection alive past the idle timeout.\n\nThis issue affects bandit: from 1.11.0 before 1.14.0."
}
],
"value": "Allocation of Resources Without Limits or Throttling vulnerability in the WebSocket fragment reassembly of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a fragmented message made of many 1-byte continuation frames.\n\nBandit.WebSocket.Connection checks max_fragmented_message_size against the payload bytes received, but keeps every non-final continuation frame as a new list cell around its own binary, and nothing limits the number of fragments. A 1-byte fragment costs 7 bytes on the wire but about 150 to 170 bytes of server memory, so one connection can hold about 150 times the configured limit, roughly 1.2 to 1.4 GB at the default 8 MB. Ping frames between fragments keep the connection alive past the idle timeout.\n\nThis issue affects bandit: from 1.11.0 before 1.14.0."
}
],
"impacts": [
{
"capecId": "CAPEC-130",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAn unauthenticated client can make one WebSocket connection hold about 150 times \u003ccode\u003emax_fragmented_message_size\u003c/code\u003e in server memory (about 82 MB for 3.5 MB of traffic in the reporter\u0027s test). This affects any Bandit server that accepts WebSocket upgrades with default settings, including Phoenix LiveView and Channels apps.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "An unauthenticated client can make one WebSocket connection hold about 150 times `max_fragmented_message_size` in server memory (about 82 MB for 3.5 MB of traffic in the reporter\u0027s test). This affects any Bandit server that accepts WebSocket upgrades with default settings, including Phoenix LiveView and Channels apps."
}
],
"value": "An unauthenticated client can make one WebSocket connection hold about 150 times max_fragmented_message_size in server memory (about 82 MB for 3.5 MB of traffic in the reporter\u0027s test). This affects any Bandit server that accepts WebSocket upgrades with default settings, including Phoenix LiveView and Channels apps."
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 8.7,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-770",
"description": "CWE-770 Allocation of Resources Without Limits or Throttling",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-26T13:30:58.262Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"name": "WebSocket 1-byte continuation frames bypass `max_fragmented_message_size` in Bandit",
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-cpx7-qf6w-jc63"
},
{
"name": "EEF CNA record for CVE-2026-114213",
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-114213.html"
},
{
"name": "OSV record EEF-CVE-2026-114213",
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-114213"
},
{
"name": "Introducing commit 21612c7 in mtrudel/bandit",
"tags": [
"related"
],
"url": "https://github.com/mtrudel/bandit/commit/21612c7c7b1ce43eccd36d3af3a2299d23513667"
},
{
"name": "Fix commit 220b9df in mtrudel/bandit",
"tags": [
"patch"
],
"url": "https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a"
}
],
"source": {
"discovery": "UNKNOWN"
},
"title": "WebSocket 1-byte continuation frames bypass `max_fragmented_message_size` in Bandit",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eLower \u003ccode\u003ewebsocket_options: [max_fragmented_message_size: ...]\u003c/code\u003e to the largest fragmented message the application needs, for example \u003ccode\u003e65_536\u003c/code\u003e. Memory per connection stays at about 150 times this limit, so a lower limit lowers the ceiling.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Lower `websocket_options: [max_fragmented_message_size: ...]` to the largest fragmented message the application needs, for example `65_536`. Memory per connection stays at about 150 times this limit, so a lower limit lowers the ceiling."
}
],
"value": "Lower websocket_options: [max_fragmented_message_size: ...] to the largest fragmented message the application needs, for example 65_536. Memory per connection stays at about 150 times this limit, so a lower limit lowers the ceiling."
}
],
"x_proofOfConcept": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003col\u003e\n\u003cli\u003eRun Bandit with default settings and a WebSock that accepts every connection.\u003c/li\u003e\n\u003cli\u003eComplete the WebSocket upgrade and send a non-final text frame with a 1-byte payload.\u003c/li\u003e\n\u003cli\u003eSend 500,000 masked non-final continuation frames with 1-byte payloads, 3.5 MB in all.\u003c/li\u003e\n\u003cli\u003eSend a Ping. The server answers with a Pong, and BEAM memory has grown by about 82 MB while the message is still far below the 8 MB cap.\u003c/li\u003e\n\u003c/ol\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "1. Run Bandit with default settings and a WebSock that accepts every connection.\n2. Complete the WebSocket upgrade and send a non-final text frame with a 1-byte payload.\n3. Send 500,000 masked non-final continuation frames with 1-byte payloads, 3.5 MB in all.\n4. Send a Ping. The server answers with a Pong, and BEAM memory has grown by about 82 MB while the message is still far below the 8 MB cap."
}
],
"value": "* Run Bandit with default settings and a WebSock that accepts every connection.\n* Complete the WebSocket upgrade and send a non-final text frame with a 1-byte payload.\n* Send 500,000 masked non-final continuation frames with 1-byte payloads, 3.5 MB in all.\n* Send a Ping. The server answers with a Pong, and BEAM memory has grown by about 82 MB while the message is still far below the 8 MB cap."
}
],
"x_technicalAnalysis": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003e\u003cstrong\u003e1. Byte-only limit.\u003c/strong\u003e In \u003ccode\u003eBandit.WebSocket.Connection\u003c/code\u003e (\u003ccode\u003elib/bandit/websocket/connection.ex\u003c/code\u003e), the fragment limit is checked against \u003ccode\u003efragment_size\u003c/code\u003e, which only adds up payload bytes (\u003ccode\u003eIO.iodata_length(frame.data)\u003c/code\u003e).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. Per-fragment accumulation.\u003c/strong\u003e Each non-final continuation frame is stored as a new cons cell around its own binary, \u003ccode\u003e[connection.fragment_frame.data | frame.data]\u003c/code\u003e. Only zero-length fragments are kept out, so 1-byte fragments are accepted. Each costs 7 bytes on the wire but keeps about 150 to 170 bytes in memory. Against 1.12.5, 1M fragments kept about 169 MB and 3M kept about 450 MB, growing linearly, and about 56 MB of traffic reaches the 8 MB payload cap.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. Kept alive.\u003c/strong\u003e Ping frames sent between fragments are handled by \u003ccode\u003ehandle_control_frame\u003c/code\u003e without touching the fragment state, so they keep the connection alive past the idle timeout.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "**1. Byte-only limit.** In `Bandit.WebSocket.Connection` (`lib/bandit/websocket/connection.ex`), the fragment limit is checked against `fragment_size`, which only adds up payload bytes (`IO.iodata_length(frame.data)`).\n\n**2. Per-fragment accumulation.** Each non-final continuation frame is stored as a new cons cell around its own binary, `[connection.fragment_frame.data | frame.data]`. Only zero-length fragments are kept out, so 1-byte fragments are accepted. Each costs 7 bytes on the wire but keeps about 150 to 170 bytes in memory. Against 1.12.5, 1M fragments kept about 169 MB and 3M kept about 450 MB, growing linearly, and about 56 MB of traffic reaches the 8 MB payload cap.\n\n**3. Kept alive.** Ping frames sent between fragments are handled by `handle_control_frame` without touching the fragment state, so they keep the connection alive past the idle timeout."
}
],
"value": "1. Byte-only limit. In Bandit.WebSocket.Connection (lib/bandit/websocket/connection.ex), the fragment limit is checked against fragment_size, which only adds up payload bytes (IO.iodata_length(frame.data)).\n\n2. Per-fragment accumulation. Each non-final continuation frame is stored as a new cons cell around its own binary, [connection.fragment_frame.data | frame.data]. Only zero-length fragments are kept out, so 1-byte fragments are accepted. Each costs 7 bytes on the wire but keeps about 150 to 170 bytes in memory. Against 1.12.5, 1M fragments kept about 169 MB and 3M kept about 450 MB, growing linearly, and about 56 MB of traffic reaches the 8 MB payload cap.\n\n3. Kept alive. Ping frames sent between fragments are handled by handle_control_frame without touching the fragment state, so they keep the connection alive past the idle timeout."
}
]
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-114213",
"datePublished": "2026-10-26T13:30:58.262Z",
"dateReserved": "2026-10-23T09:15:01.838Z",
"dateUpdated": "2026-10-26T15:35:51.785Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.