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TI-2026-28690 Aliases CVE-2026-39807GHSA-375f-4r2h-f99j

Client-supplied URI scheme trusted without transport verification in bandit

Priority HIGH 67CWE-807Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
Present
Impact type
—
Confidentiality · integrity · availability
Low · Low · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub.

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00531 45th percentileScored 2026-11-07
Fix Fixed bandit (mtrudel): 1.11.0bandit (Hex): 1.11.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
mtrudelbandit1.0.0 to before 1.11.01.11.0Patch availableCNA
—bandit (Hex)1.0.0 to before 1.11.01.11.0Patch availableGHSA-375f-4r2h-f99j
  • bandit Vendormtrudel Affected 1.0.0 to before 1.11.0 Fixed in 1.11.0 Patch available CNA
  • bandit (Hex) Vendor— Affected 1.0.0 to before 1.11.0 Fixed in 1.11.0 Patch available GHSA-375f-4r2h-f99j

CPE names CNA · 1

CPEVersionsRoleVendor
cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*——mtrudel
  • cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:* Versions — — ·mtrudel

Remediation

  • Fix · CNA bandit (mtrudel) Fixed in 1.11.0
  • Fix · GHSA-375f-4r2h-f99j bandit (Hex) Fixed in 1.11.0 Advisory →

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    mtrudel bandit 1.11.0

    5 records Highest priority Priority HIGH 5 HIGH

    Other records, highest priority first

    • TI-2026-31007 WebSocket fragmented message reassembly unbounded in banditPriority HIGH 77
    • TI-2026-28687 WebSocket permessage-deflate inflate has no output-size cap in banditPriority HIGH 75
    • TI-2026-31008 HTTP/2 frame size limit checked after body is buffered in banditPriority HIGH 70
    Show all 5 records →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-39807
  2. 2026-10-03 Alias added: GHSA-375f-4r2h-f99j

References

Patch 1

Advisory 2

Other 3

  • TI-2026-81989 HTTP/2 request bodies made of 1-byte DATA frames amplify memory use in Bandit CVSS 4.0HIGH 8.7
  • TI-2026-74311 Bandit HTTP/2 send timers reset, letting trickles pin stream processes CVSS 4.0HIGH 8.7
  • TI-2026-52571 HTTP/2 connection-window starvation pins Plug processes indefinitely in Bandit CVSS 4.0HIGH 8.7
  • TI-2026-46780 Quadratic CPU blow-up reassembling fragmented WebSocket messages in Bandit CVSS 4.0HIGH 8.7
  • TI-2026-31007 WebSocket fragmented message reassembly unbounded in bandit CVSS 4.0HIGH 8.7
  • TI-2026-28689 HTTP/1 chunked decoder infinite loop on requests with trailer fields in bandit CVSS 4.0HIGH 8.7
See all 23 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences