Read the docs
TI-2020-12443 Aliases CVE-2020-15811

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4.

Priority LOW 36CWE-697Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · High · None
Fix status
Partial Red Hat: 7 fixed, 2 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat.

Summary

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.

Why it matters now

EPSS 0.04069 90th percentileScored 2026-11-07
Fix Partial Red Hat: 2 advisoriesRed Hat: 7 fixed, 2 without a fix

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
——all versions—No fix listedCNA
  • — Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 11

CPEVersionsRoleVendor
cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*before 4.13; 5.0 to before 5.0.4Vulnerablesquid-cache
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*16.04VulnerableCanonical
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*18.04VulnerableCanonical
cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*20.04VulnerableCanonical
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*9.0VulnerableDebian
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*10.0VulnerableDebian
cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*31VulnerableFedoraproject
cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*32VulnerableFedoraproject
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*33VulnerableFedoraproject
cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*15.1VulnerableopenSUSE
  • cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:* Versions before 4.13; 5.0 to before 5.0.4 Vulnerable ·squid-cache
  • cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:* Versions 16.04 Vulnerable ·Canonical
  • cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:* Versions 18.04 Vulnerable ·Canonical
  • cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:* Versions 20.04 Vulnerable ·Canonical
  • cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* Versions 9.0 Vulnerable ·Debian
  • cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian
  • cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:* Versions 31 Vulnerable ·Fedoraproject
  • cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:* Versions 32 Vulnerable ·Fedoraproject
  • cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* Versions 33 Vulnerable ·Fedoraproject
  • cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:* Versions 15.1 Vulnerable ·openSUSE
Show 1 more CPE
CPEVersionsRoleVendor
cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*15.2VulnerableopenSUSE
  • cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:* Versions 15.2 Vulnerable ·openSUSE

Remediation

Red Hat 2 advisories

  • RHSA-2020:4082 Released 2020-09-30 · Red Hat rating Important
    squid security update
    • Red Hat Enterprise Linux Server (v. 7) squid-7:3.5.20-17.el7_9.4, squid-migration-script-7:3.5.20-17.el7_9.4
    • Red Hat Enterprise Linux Server Optional (v. 7) squid-sysvinit-7:3.5.20-17.el7_9.4
    • Red Hat Enterprise Linux Workstation (v. 7) squid-7:3.5.20-17.el7_9.4, squid-migration-script-7:3.5.20-17.el7_9.4
    • Red Hat Enterprise Linux Workstation Optional (v. 7) squid-sysvinit-7:3.5.20-17.el7_9.4
  • RHSA-2020:3623 Released 2020-09-03 · Red Hat rating Important
    squid:4 security update
    • Red Hat Enterprise Linux AppStream (v. 8) libecap-1.0.1-2.module+el8.1.0+4044+36416a77.aarch64::squid:4, libecap-1.0.1-2.module+el8.1.0+4044+36416a77.ppc64le::squid:4, libecap-1.0.1-2.module+el8.1.0+4044+36416a77.s390x::squid:4 +11
    • Red Hat Enterprise Linux AppStream E4S (v. 8.0) libecap-1.0.1-2.module+el8.0.0+4045+70edde92.ppc64le::squid:4, libecap-1.0.1-2.module+el8.0.0+4045+70edde92.src::squid:4, libecap-1.0.1-2.module+el8.0.0+4045+70edde92.x86_64::squid:4 +5
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) libecap-1.0.1-2.module+el8.1.0+4044+36416a77.aarch64::squid:4, libecap-1.0.1-2.module+el8.1.0+4044+36416a77.ppc64le::squid:4, libecap-1.0.1-2.module+el8.1.0+4044+36416a77.s390x::squid:4 +11

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 5AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2020:3623
Red Hat Enterprise Linux AppStream E4S (v. 8.0)Fixed RHSA-2020:3623
Red Hat Enterprise Linux AppStream EUS (v. 8.1)Fixed RHSA-2020:3623
Red Hat Enterprise Linux Server (v. 7)Fixed RHSA-2020:4082
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2020:4082
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2020:4082
Red Hat Enterprise Linux Workstation Optional (v. 7)Fixed RHSA-2020:4082

Timeline

  1. 2026-10-02 Threatist record created from CVE-2020-15811

References

Patch 1

Advisory 12

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences