{"document":{"category":"csaf_vex","csaf_version":"2.0","title":"CVE-2026-55203: HAProxy - Integer Overflow in FCGI Demux Record Length Field","publisher":{"category":"vendor","name":"HarborGuard Database","namespace":"https://database.harborguard.co"},"tracking":{"id":"CVE-2026-55203","status":"final","version":"1","initial_release_date":"2026-06-18T16:05:20.100Z","current_release_date":"2026-06-18T16:05:20.100Z","revision_history":[{"date":"2026-06-18T16:05:20.100Z","number":"1","summary":"Initial machine-readable export from HarborGuard."}]},"distribution":{"tlp":{"label":"WHITE"},"text":"Public CVE data; freely redistributable."},"notes":[{"category":"description","text":"HAProxy through 3.4.0, fixed in commit 5985276, contains an integer overflow vulnerability in the fcgi_conn structure's drl field that allows buffer misparse as new FCGI record headers. When contentLength is 65535 and paddingLength is 1 or more, the drl field wraps to 0, causing incorrect record consumption and allowing malicious FastCGI backends to desynchronize the FCGI framing parser, potentially causing request routing errors, response smuggling, or memory safety issues.","title":"CVE description"}],"references":[{"category":"self","summary":"CVE-2026-55203 on HarborGuard Database","url":"https://database.harborguard.co/cve/CVE-2026-55203"},{"category":"external","summary":"CVE Record","url":"https://www.cve.org/CVERecord?id=CVE-2026-55203"},{"category":"external","summary":"Patch Commit","url":"https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd"},{"category":"external","summary":"vulncheck.com","url":"https://www.vulncheck.com/advisories/haproxy-integer-overflow-in-fcgi-demux-record-length-field"}]},"product_tree":{"branches":[{"category":"vendor","name":"haproxy","branches":[{"category":"product_name","name":"haproxy","branches":[{"category":"product_version_range","name":"<=3.4.0","product":{"name":"haproxy haproxy <=3.4.0","product_id":"CSAFPID-1","product_identification_helper":{"cpe":"cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"5985276735777634d8c85f1d73bb7764aab0d6dd","product":{"name":"haproxy haproxy 5985276735777634d8c85f1d73bb7764aab0d6dd","product_id":"CSAFPID-2","product_identification_helper":{"cpe":"cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*"}}}]}]}]},"vulnerabilities":[{"cve":"CVE-2026-55203","title":"HAProxy - Integer Overflow in FCGI Demux Record Length Field","notes":[{"category":"description","text":"HAProxy through 3.4.0, fixed in commit 5985276, contains an integer overflow vulnerability in the fcgi_conn structure's drl field that allows buffer misparse as new FCGI record headers. When contentLength is 65535 and paddingLength is 1 or more, the drl field wraps to 0, causing incorrect record consumption and allowing malicious FastCGI backends to desynchronize the FCGI framing parser, potentially causing request routing errors, response smuggling, or memory safety issues.","title":"CVE description"}],"product_status":{"known_affected":["CSAFPID-1"],"fixed":["CSAFPID-2"]},"scores":[{"cvss_v4":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N","baseScore":9,"baseSeverity":"CRITICAL"},"products":["CSAFPID-1"]}],"remediations":[{"category":"vendor_fix","details":"Update to a fixed version: 5985276735777634d8c85f1d73bb7764aab0d6dd.","product_ids":["CSAFPID-1"],"url":"https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd"}]}]}