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Vulnerability record · CVE-2020-15810 · published 2 September 2020

CVE-2020-15810: Squid-cache squid http request smuggling vulnerability

Squid Cache · Squid

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Smuggling 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 proxy cache and any downstream caches with content from an arbitrary source. When configured for relaxed header parsing (the default), Squid relays headers containing whitespace characters to upstream servers. When this occurs as a prefix to a Content-Length header, the frame length specified will be ignored by Squid (allowing for a conflicting length to be used from another Content-Length header) but relayed upstream.

6.5 CVSS 3.1 Medium EPSS 2.4% · top 16.3% CWE-444 · HTTP request smuggling
6.5CVSS 3.1 base score, v2 3.5
2.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
5Affected product versions listed by NVD
26References
17 Jun 2026Last modified by NVD

Description

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Smuggling 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 proxy cache and any downstream caches with content from an arbitrary source. When configured for relaxed header parsing (the default), Squid relays headers containing whitespace characters to upstream servers. When this occurs as a prefix to a Content-Length header, the frame length specified will be ignored by Squid (allowing for a conflicting length to be used from another Content-Length header) but relayed upstream.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Affected products

5 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00012.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00017.html Mailing ListThird Party Advisory
https://github.com/squid-cache/squid/security/advisories/GHSA-3365-q9qx-f98m MitigationThird Party Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00005.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BE6FKUN7IGTIR2MEEMWYDT7
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMTFLVB7GLRF2CKGFPZ4G4R
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HJJDI7JQFGQLVNCKMVY64LA
https://security.netapp.com/advisory/ntap-20210219-0007/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20210226-0006/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20210226-0007/ Broken Link
https://usn.ubuntu.com/4477-1/ Third Party Advisory
https://usn.ubuntu.com/4551-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4751 Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00012.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00017.html Mailing ListThird Party Advisory
https://github.com/squid-cache/squid/security/advisories/GHSA-3365-q9qx-f98m MitigationThird Party Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00005.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BE6FKUN7IGTIR2MEEMWYDT7
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMTFLVB7GLRF2CKGFPZ4G4R
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HJJDI7JQFGQLVNCKMVY64LA
https://security.netapp.com/advisory/ntap-20210219-0007/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20210226-0006/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20210226-0007/ Broken Link
https://usn.ubuntu.com/4477-1/ Third Party Advisory
https://usn.ubuntu.com/4551-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4751 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-15810), CISA KEV, FIRST EPSS (scores of 2026-10-07). This page is refreshed as NVD updates the record.