Vulnerability in Squid-Cache Squid
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.
EPSS: 0.042 (90.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.
Affected products
- Squid-cache Squid
- Canonical Ubuntu_linux — versions 16.04, 18.04, 20.04
- Debian Debian_linux — versions 9.0, 10.0
- Fedoraproject Fedora — versions 31, 32, 33
- Opensuse Leap — versions 15.1, 15.2
- N/a — versions n/a
Weakness classification (CWE)
Public proof-of-concept exploits
References
- cve@mitre.org (Patch, x_refsource_MISC)
- cve@mitre.org (vendor-advisory, Mailing List, Third Party Advisory, x_refsource_DEBIAN)
- cve@mitre.org (x_refsource_UBUNTU, vendor-advisory, Third Party Advisory)
- cve@mitre.org (x_refsource_FEDORA, vendor-advisory, Mailing List, Third Party Advisory)
- cve@mitre.org (x_refsource_FEDORA, vendor-advisory, Mailing List, Third Party Advisory)
- cve@mitre.org (vendor-advisory, Mailing List, Third Party Advisory, x_refsource_SUSE)
- cve@mitre.org (vendor-advisory, Mailing List, Third Party Advisory, x_refsource_SUSE)
- cve@mitre.org (x_refsource_FEDORA, vendor-advisory, Mailing List, Third Party Advisory)
- cve@mitre.org (x_refsource_UBUNTU, vendor-advisory, Third Party Advisory)
- cve@mitre.org (mailing-list, x_refsource_MLIST, Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2020-15811?
- CVE-2020-15811 is a medium-severity vulnerability in Squid-Cache Squid, classified under Incorrect Comparison. CVSS score: 6.5/10. Published 2020-09-02.
- How severe is CVE-2020-15811?
- Medium severity. CVSS v3 base score is 6.5 out of 10.
- Is CVE-2020-15811 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.