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.
CWE
  • CWE-807 - Reliance on Untrusted Inputs in a Security Decision
Assigner
EEF
Impacted products
Vendor Product Version
mtrudel bandit Affected: 1.0.0 , < 1.11.0 (semver)
    cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*
Create a notification for this product.
    mtrudel bandit Affected: ff2f829326cd5dcf7335939aef9775269d881e28 , < 45feea20dea8af7ffd7245271107b695c040e667 (git)
    cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*
Create a notification for this product.
Credits
Peter Ullrich Mat Trudel Jonatan Männchen
Show details on NVD website

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HTTP/1.1 absolute-form request targets (e.g. \u003ctt\u003eGET https://victim/path HTTP/1.1\u003c/tt\u003e) and the HTTP/2 \u003ctt\u003e:scheme\u003c/tt\u003e pseudo-header are both attacker-controlled strings that flow through this function. Over a plaintext TCP connection, a client can declare \u003ctt\u003ehttps\u003c/tt\u003e and Bandit will set \u003ctt\u003econn.scheme = :https\u003c/tt\u003e even though no TLS was negotiated.\u003c/p\u003e\u003cp\u003eDownstream Plug consumers that branch on \u003ctt\u003econn.scheme\u003c/tt\u003e are silently misled: \u003ctt\u003ePlug.SSL\u003c/tt\u003e\u0027s already-secure branch skips its HTTP\\u2192HTTPS redirect, cookies emitted with \u003ctt\u003esecure: true\u003c/tt\u003e are sent over plaintext, audit logs record requests as having arrived over HTTPS, and CSRF/SameSite gating may make incorrect decisions.\u003c/p\u003e\u003cp\u003eThis issue affects bandit: from 1.0.0 before 1.11.0.\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-807\", \"description\": \"CWE-807 Reliance on Untrusted Inputs in a Security Decision\"}]}], \"configurations\": [{\"lang\": \"en\", \"value\": \"The vulnerable system must be accepting plaintext (non-TLS) HTTP connections, either directly or via h2c. Deployments that exclusively use TLS are not affected.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eThe vulnerable system must be accepting plaintext (non-TLS) HTTP connections, either directly or via h2c. Deployments that exclusively use TLS are not affected.\u003c/p\u003e\", \"base64\": false}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"1.11.0\", \"versionStartIncluding\": \"1.0.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-05-04T17:11:38.567Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-39807\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-04T17:11:38.567Z\", \"dateReserved\": \"2026-04-07T12:28:54.916Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-05-01T20:34:22.832Z\", \"assignerShortName\": \"EEF\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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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.


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Detection rules are retrieved from Rulezet.

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