CVE-2020-15811
MEDIUMCVSS 6.5/10EPSS 4.23%
Last modified
CVE-2020-15811 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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. EPSS estimates a 4.23% chance of exploitation in the next 30 days.
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Squid-Cache | Squid | < 4.13 |
| Squid-Cache | Squid | >= 5.0, < 5.0.4 |
| Canonical | Ubuntu Linux | 16.04 |
| Canonical | Ubuntu Linux | 18.04 |
| Canonical | Ubuntu Linux | 20.04 |
| Debian | Debian Linux | 9.0 |
| Debian | Debian Linux | 10.0 |
| Fedoraproject | Fedora | 31 |
| Fedoraproject | Fedora | 32 |
| Fedoraproject | Fedora | 33 |
| Opensuse | Leap | 15.1 |
| Opensuse | Leap | 15.2 |
References
- http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00012.htmlMailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00017.htmlMailing List, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/10/msg00005.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BE6FKUN7IGTIR2MEEMWYDT7N5EJJLZI2/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMTFLVB7GLRF2CKGFPZ4G4R5DIIPHWI3/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HJJDI7JQFGQLVNCKMVY64LAFMKERAOK7/Mailing List, Third 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 Link, Third 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-4751Mailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00012.htmlMailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00017.htmlMailing List, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/10/msg00005.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BE6FKUN7IGTIR2MEEMWYDT7N5EJJLZI2/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMTFLVB7GLRF2CKGFPZ4G4R5DIIPHWI3/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HJJDI7JQFGQLVNCKMVY64LAFMKERAOK7/Mailing List, Third 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 Link, Third 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-4751Mailing List, Third Party Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2020-15811?
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.
How severe is CVE-2020-15811?
CVE-2020-15811 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 4.23% probability of exploitation in the next 30 days.
How do I fix CVE-2020-15811?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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Are you affected by CVE-2020-15811?
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