Request smuggling via first-wins Content-Length parsing
Published Mar 13, 2026 · Updated Mar 13, 2026
HTTP request smuggling in Erlang/OTP inets httpd allows remote attackers to access protected backend resources via crafted requests. httpd_request:parse_headers/7 accepts conflicting duplicate Content-Length headers and uses the first value, while a last-wins frontend can delimit the body differently and queue attacker-controlled bytes as a new request. Exploitation requires httpd behind a differently parsing proxy, load balancer, or CDN with keep-alive enabled; successful desynchronization enables authentication bypass, cache poisoning, or request hijacking.
Summary
What happened
HTTP request smuggling in Erlang/OTP inets httpd allows remote attackers to access protected backend resources via crafted requests. httpd_request:parse_headers/7 accepts conflicting duplicate Content-Length headers and uses the first value, while a last-wins frontend can delimit the body differently and queue attacker-controlled bytes as a new request. Exploitation requires httpd behind a differently parsing proxy, load balancer, or CDN with keep-alive enabled; successful desynchronization enables authentication bypass, cache poisoning, or request hijacking.
The record
- CVE
- CVE-2026-23941
- Published
- Mar 13, 2026
- Updated
- Mar 13, 2026
- Vendor
- Erlang
- Product
- Erlang/OTP
- Classifications
- CWE-444, CAPEC-33, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 13, 2026CVE publishedPublication date reported by the CVE source.
- Mar 13, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <* changes=[{"at":"a4b46336fd25aa100ac602eb9a627aaead7eda18","status":"unaffected"},{"at":"a761d391d8d08316cbd7d4a86733ba932b73c45b","status":"unaffected"},{"at":"e775a332f623851385ab6ddb866d9b150612ddf6","status":"unaffected"}]
- Affected versionversion=17.0 <* changes=[{"at":"28.4.1","status":"unaffected"},{"at":"27.3.4.9","status":"unaffected"},{"at":"26.2.5.18","status":"unaffected"}]
- Affected versionversion=5.10 <* changes=[{"at":"9.6.1","status":"unaffected"},{"at":"9.3.2.3","status":"unaffected"},{"at":"9.1.0.5","status":"unaffected"}]
- Affected versionversion=pkg:otp/[email protected] <pkg:otp/inets@* changes=[{"at":"pkg:otp/[email protected]","status":"unaffected"},{"at":"pkg:otp/[email protected]","status":"unaffected"},{"at":"pkg:otp/[email protected]","status":"unaffected"}]
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What is affected?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
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Technologies
Your stack
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Your stack
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