Request smuggling via empty Content-Length forwarding
Published Aug 10, 2023 · Updated Oct 9, 2024
HTTP request smuggling in HAProxy allows remote attackers to bypass proxy inspection through crafted HTTP/1 requests with conflicting lengths. The h1_parse_cont_len_header and http_parse_cont_len_header parsers treat an empty Content-Length value as absent, so HAProxy forwards it beside a valid value. Exploitation requires a noncompliant HTTP/1 backend that interprets the empty value as zero and consumes the payload as another request.
Summary
What happened
HTTP request smuggling in HAProxy allows remote attackers to bypass proxy inspection through crafted HTTP/1 requests with conflicting lengths. The h1_parse_cont_len_header and http_parse_cont_len_header parsers treat an empty Content-Length value as absent, so HAProxy forwards it beside a valid value. Exploitation requires a noncompliant HTTP/1 backend that interprets the empty value as zero and consumes the payload as another request.
The record
- CVE
- CVE-2023-40225
- Published
- Aug 10, 2023
- Updated
- Oct 9, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-444, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 10, 2023CVE publishedPublication date reported by the CVE source.
- Oct 9, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- HAProxy forwards malformed empty Content-Length headers, in violation of RFC 9110proof of concept · demonstrated
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Technologies
Your stack
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Your stack
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