CL.CL HTTP request smuggling via duplicate Content-Length in bandit

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Summary

CVECVE-2026-39805
StatePUBLISHED
AssignerEEF
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-01 21:16:17 UTC
Updated2026-05-02 02:16:00 UTC
DescriptionInconsistent Interpretation of HTTP Requests vulnerability in mtrudel bandit allows HTTP request smuggling via duplicate Content-Length headers. 'Elixir.Bandit.Headers':get_content_length/1 in lib/bandit/headers.ex uses List.keyfind/3, which returns only the first matching header. When a request contains two Content-Length headers with different values, Bandit silently accepts it, uses the first value to read the body, and dispatches the remaining bytes as a second pipelined request on the same keep-alive connection. RFC 9112 §6.3 requires recipients to treat this as an unrecoverable framing error. When Bandit sits behind a proxy that picks the last Content-Length value and forwards the request rather than rejecting it, an unauthenticated attacker can smuggle requests past edge WAF rules, path-based ACLs, rate limiting, and audit logging. This issue affects bandit: before 1.11.0.

Risk And Classification

Primary CVSS: v4.0 6.3 MEDIUM from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-444 | CWE-444 CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

VersionSourceTypeScoreSeverityVector
4.06b3ad84c-e1a6-4bf7-a703-f496b71e49dbSecondary6.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS6.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mtrudel Bandit affected 1.11.0 semver Not specified
CNA Mtrudel Bandit affected 1.11.0 git Not specified

References

ReferenceSourceLinkTags
github.com/mtrudel/bandit/commit/f2ca636eb6df385219957e8934e9fc6efa1630d1 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
osv.dev/vulnerability/EEF-CVE-2026-39805 6b3ad84c-e1a6-4bf7-a703-f496b71e49db osv.dev
github.com/mtrudel/bandit/security/advisories/GHSA-c67r-gc9j-2qf7 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
cna.erlef.org/cves/CVE-2026-39805.html 6b3ad84c-e1a6-4bf7-a703-f496b71e49db cna.erlef.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Peter Ullrich (en)

CNA: Mat Trudel (en)

CNA: Jonatan Männchen (en)

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