{"cve":"CVE-2020-15811","nvd":{"published":"2020-09-02T17:15:11.687","modified":"2026-06-17T02:57:14.090","status":"Modified","description":"An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","score":6.5},"cwes":["CWE-697"],"references":["http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00012.html","http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00017.html","https://github.com/squid-cache/squid/security/advisories/GHSA-c7p8-xqhm-49wv","https://lists.debian.org/debian-lts-announce/2020/10/msg00005.html","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BE6FKUN7IGTIR2MEEMWYDT7N5EJJLZI2/"],"products":["canonical:ubuntu_linux","debian:debian_linux","fedoraproject:fedora","opensuse:leap","squid-cache:squid"],"source":"nvd","synced_at":"2026-10-19T21:09:20.498348299+00:00"},"epss":{"cve":"CVE-2020-15811","score":0.04069,"percentile":0.90678,"date":"2026-11-01"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}