EEF-CVE-2026-39805 CVE-2026-39805 GHSA-c67r-gc9j-2qf7
CL.CL HTTP request smuggling via duplicate Content-Length in bandit
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.63%
- Chance of exploitation in the next 30 days. Higher than 50.04% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
- Fix
1.11.0- Upgrade bandit to this version or later
Description
Summary
Inconsistent 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.
Affected versions
Hex
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
bandit Hex → 1.11.0
- mix
{:bandit, "~> 1.11.0"} # then: mix deps.update bandit
Severity breakdown
CVSS 4.0 0.0
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
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- Low
- Integrity (vulnerable system)
- Low
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
Weakness
CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
How to prevent it
- Implementation: Use a web server that employs a strict HTTP parsing procedure, such as Apache [REF-433].
- Implementation: Use only SSL communication.
- Implementation: Terminate the client session after each request.
- System Configuration: Turn all pages to non-cacheable.
References
Advisories
Fixes and patches
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| EEF-CVE-2026-116078 HTTP/2 request bodies made of 1-byte DATA frames amplify memory use in Bandit | Not rated yet | Also affects bandit |
| EEF-CVE-2026-108529 SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in Bandit | Not rated yet | Also affects bandit |
| EEF-CVE-2026-110499 Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Bandit | Not rated yet | Also affects bandit |
| EEF-CVE-2026-109584 HTTP/2 cookie crumb join expands a small HPACK header block into an unbounded allocation in Bandit | Not rated yet | Also affects bandit |
| EEF-CVE-2026-111103 HTTP/2 StreamError recovery rolls back connection state and bypasses per-connection limits in Bandit | Not rated yet | Also affects bandit |
| EEF-CVE-2026-111101 HTTP/1.1 chunked request bodies made of 1-byte chunks amplify memory use in Bandit | Not rated yet | Also affects bandit |
| EEF-CVE-2026-113436 Quadratic bignum parsing of Content-Length and Host port values in Bandit | Not rated yet | Also affects bandit |
| EEF-CVE-2026-110314 WebSocket frames keep reaching the WebSock after a server-initiated close in Bandit | Not rated yet | Also affects bandit |
Credits: Jonatan Männchen / EEF, Mat Trudel, Peter Ullrich
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