CVE-2026-42786

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Source
https://cve.org/CVERecord?id=CVE-2026-42786
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42786.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-42786
Aliases
Published
2026-05-01T20:34:17.014Z
Modified
2026-07-08T08:12:35.238052365Z
Severity
  • 8.7 (High) CVSS_V4 - 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 CVSS Calculator
Summary
WebSocket fragmented message reassembly unbounded in bandit
Details

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':handleframe/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 maxframe_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.

Database specific 
{
    "unresolved_ranges": [
        {
            "source": "AFFECTED_FIELD",
            "extracted_events": [
                {
                    "introduced": "8909391f486d42138c5308410bc5ea49a65f4d46"
                },
                {
                    "fixed": "21612c7c7b1ce43eccd36d3af3a2299d23513667"
                }
            ]
        }
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42786.json",
    "cna_assigner": "EEF",
    "cwe_ids": [
        "CWE-770"
    ]
}
References

Affected packages

Git / github.com/mtrudel/bandit

Affected ranges

Type
GIT
Repo
https://github.com/mtrudel/bandit
Events
Introduced
102adfd56bd4aacd39469a5582104377618abc9f
Fixed
e62619895d0d2584d7ffa57d43ef6f72437dfaff
Fixed
21612c7c7b1ce43eccd36d3af3a2299d23513667
Database specific 
{
    "source": [
        "DESCRIPTION",
        "REFERENCES"
    ],
    "extracted_events": [
        {
            "introduced": "0.5.0"
        },
        {
            "fixed": "1.11.0"
        }
    ]
}

Affected versions

0.*
0.5.0
0.5.1
0.5.10
0.5.11
0.5.2
0.5.3
0.5.4
0.5.5
0.5.6
0.5.7
0.5.8
0.5.9
0.6.0
0.6.1
0.6.10
0.6.11
0.6.2
0.6.3
0.6.4
0.6.5
0.6.6
0.6.7
0.6.8
0.6.9
0.7.0
0.7.1
0.7.2
0.7.3
0.7.4
0.7.5
0.7.6
0.7.7
1.*
1.0.0
1.0.0-pre.1
1.0.0-pre.10
1.0.0-pre.11
1.0.0-pre.12
1.0.0-pre.13
1.0.0-pre.14
1.0.0-pre.15
1.0.0-pre.16
1.0.0-pre.17
1.0.0-pre.18
1.0.0-pre.2
1.0.0-pre.3
1.0.0-pre.4
1.0.0-pre.5
1.0.0-pre.6
1.0.0-pre.7
1.0.0-pre.8
1.0.0-pre.9
1.1.0
1.1.1
1.1.2
1.1.3
1.10.0
1.10.1
1.10.2
1.10.3
1.10.4
1.2.0
1.2.3
1.3.0
1.4.0
1.4.1
1.4.2
1.5.0
1.5.1
1.5.2
1.5.3
1.5.4
1.5.5
1.5.6
1.5.7
1.6.0
1.6.1
1.6.10
1.6.11
1.6.2
1.6.3
1.6.4
1.6.5
1.6.6
1.6.7
1.6.8
1.6.9
1.7.0
1.8.0
1.9.0

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42786.json"