CVE-2026-39806

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Source

https://cve.org/CVERecord?id=CVE-2026-39806

Import Source

https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-39806.json

JSON Data

https://api.osv.dev/v1/vulns/CVE-2026-39806

Aliases

Published

2026-05-13T13:36:17.806Z

Modified

2026-07-08T08:13:03.389166556Z

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

HTTP/1 chunked decoder infinite loop on requests with trailer fields in bandit

Details

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in mtrudel bandit allows unauthenticated remote denial of service via worker process exhaustion.

'Elixir.Bandit.HTTP1.Socket':doreadchunkeddata!/5 in lib/bandit/http1/socket.ex terminates only when the last-chunk line 0\r\n is followed immediately by the empty trailer line \r\n. RFC 9112 §7.1.2 permits zero or more trailer fields between them. When trailers are present, none of the match clauses fit: the catch-all arm computes a negative toread, calls read_available!/2, receives <<>> on timeout, and tail-recurses with unchanged state. The worker process is pinned for the lifetime of the TCP connection.

A handful of concurrent connections sending RFC-conformant chunked requests with trailer fields is sufficient to exhaust the Bandit worker pool and render the server unresponsive to all further traffic. No authentication, special headers, or large payload is required. Proxies such as NGINX and HAProxy legitimately forward trailer-bearing requests, so servers behind such proxies may be affected without any malicious client involvement.

This issue affects bandit: from 1.6.1 before 1.11.1.

Database specific

{
    "cna_assigner": "EEF",
    "cwe_ids": [
        "CWE-835"
    ],
    "unresolved_ranges": [
        {
            "extracted_events": [
                {
                    "introduced": "e73e379ab59840e8561b5730878f16e29ab06217"
                },
                {
                    "fixed": "ae3520dfdbfab115c638f8c7f6f6b805db34e1ab"
                }
            ],
            "source": "AFFECTED_FIELD"
        }
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39806.json"
}

References

Affected packages

Git / github.com/mtrudel/bandit

Affected ranges

Type

GIT

Repo

https://github.com/mtrudel/bandit

Events

Introduced

9d86e2756b69dce50cbede6cdc7d0732b28e7276

Fixed

40a1b8fc924694a0125bbaa7fee101fa43feeb52

Fixed

ae3520dfdbfab115c638f8c7f6f6b805db34e1ab

Database specific

{
    "extracted_events": [
        {
            "introduced": "1.6.1"
        },
        {
            "fixed": "1.11.1"
        }
    ],
    "cpe": "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*",
    "source": [
        "CPE_RANGE",
        "REFERENCES"
    ]
}

Affected versions

1.*

1.10.0

1.10.1

1.10.2

1.10.3

1.10.4

1.11.0

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-2026-39806.json"