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Vulnerability record · CVE-2020-15811 · published 2 September 2020

CVE-2020-15811: Squid-cache squid 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 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.

6.5 CVSS 3.1 Medium EPSS 4.1% · top 9.6% CWE-697 · CWE-697
6.5CVSS 3.1 base score, v2 4.0
4.1%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 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: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-c7p8-xqhm-49wv Patch
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 Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMTFLVB7GLRF2CKGFPZ4G4R Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HJJDI7JQFGQLVNCKMVY64LA Mailing ListThird Party Advisory
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 LinkThird Party Advisory
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 Mailing ListThird 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-c7p8-xqhm-49wv Patch
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 Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMTFLVB7GLRF2CKGFPZ4G4R Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HJJDI7JQFGQLVNCKMVY64LA Mailing ListThird Party Advisory
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 LinkThird Party Advisory
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 Mailing ListThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-15811), CISA KEV, FIRST EPSS (scores of 2026-10-06). This page is refreshed as NVD updates the record.