HTTP request smuggling in Squid

This security advisory describes one medium risk vulnerability.

1) Inconsistent interpretation of HTTP requests

Risk: Medium

CVSSv3: 6.3 [CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N/E:U/RL:O/RC:C] [PCI]

CVE-ID: CVE-2020-25097

CWE-ID: CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling')

Exploit availability: No


The vulnerability allows a remote attacker to preform HTTP request smuggling attacks.

The vulnerability exists due to improper validation of HTTP requests. A remote attacker can send a specially crafted HTTP request to the server and smuggle arbitrary HTTP headers.

Successful exploitation of vulnerability may allow an attacker to poison HTTP cache and perform phishing attacks.


Install updates from vendor's website.

Vulnerable software versions

Squid: 2.0, 2.0.patch1, 2.0.patch2, 2.0.pre1, 2.0.release, 2.0_patch2, 2.1, 2.1.patch1, 2.1.patch2, 2.1.pre1, 2.1.pre3, 2.1.pre4, 2.1.release, 2.1_patch2, 2.2, 2.2.devel3, 2.2.devel4, 2.2.pre1, 2.2.pre2, 2.2.stable1, 2.2.stable2, 2.2.stable3, 2.2.stable4, 2.2.stable5, 2.3, 2.3.devel2, 2.3.devel3, 2.3.stable1, 2.3.stable2, 2.3.stable3, 2.3.stable4, 2.3.stable5, 2.3_.stable4, 2.3_.stable5, 2.3_stable5, 2.4, 2.4.stable1, 2.4.stable2, 2.4.stable3, 2.4.stable4, 2.4.stable5, 2.4.stable6, 2.4.stable7, 2.4_.stable2, 2.4_.stable6, 2.4_.stable7, 2.4_9, 2.4_stable7, 2.4_stable_2, 2.4_stable_3, 2.5, 2.5.6, 2.5.9, 2.5.stable1, 2.5.stable2, 2.5.stable3, 2.5.stable4, 2.5.stable5, 2.5.stable6, 2.5.stable7, 2.5.stable8, 2.5.stable9, 2.5.stable10, 2.5.stable11, 2.5.stable12, 2.5.stable13, 2.5.stable14, 2.5_.stable1, 2.5_.stable3, 2.5_.stable4, 2.5_.stable5, 2.5_.stable6, 2.5_stable3, 2.5_stable4, 2.5_stable9, 2.6, 2.6.stable1, 2.6.stable2, 2.6.stable3, 2.6.stable4, 2.6.stable5, 2.6.stable6, 2.6.stable7, 2.6.stable8, 2.6.stable9, 2.6.stable10, 2.6.stable11, 2.6.stable12, 2.6.stable13, 2.6.stable14, 2.6.stable15, 2.6.stable16, 2.6.stable17, 2.6.stable18, 2.6.stable19, 2.6.stable20, 2.6.stable21, 2.6.stable22, 2.6.stable23, 2.6.stable24, 2.7, 2.7.RC2, 2.7.stable1, 2.7.stable2, 2.7.stable3, 2.7.stable4, 2.7.stable5, 2.7.STABLE6, 2.7.STABLE7, 2.7. ..