CVE-2020-15811: canonical ubuntu_linux Incorrect Comparison
Vulnerability summary
CVE-2020-15811 is a medium (CVSS 6.5) Incorrect Comparison vulnerability in canonical ubuntu_linux. EPSS estimates a 4.07% chance of exploitation in the next 30 days, higher than 90.5% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 14 · Related 9Timeline
- 02-09-2020PublishedVulnerability first disclosed.
- 04-08-2024Last modifiedVulnerability information updated.
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 metrics
5 scores · 4 sources · 2 versions- OSV · AlpineEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
EPSS trend
Probability
4.07%
Chance of exploitation in the next 30 days
Percentile
91%
Versus all other CVEs
30-day change
-0.17 pp
From 4.23% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian2 products
- squid< 4.13-1
- debian_linuxEOL9.0 | 10.0
Ubuntu2 products
- squid< 4.10-1ubuntu1.2
- squid3< 3.5.12-1ubuntu7.15 | < 3.5.27-1ubuntu1.9
Alpine1 product
- squid≥ 5.0, < 4.13-r0 | ≥ 5.0, < 4.13.0-r0
Canonical1 product
- ubuntu_linuxEOL16.04 | 18.04 | 20.04
Fedoraproject1 product
- fedoraEOL31 | 32 | 33
Opensuse1 product
- leapEOL15.1 | 15.2
Squid-cache1 product
- squid< 4.13 | ≥ 5.0, < 5.0.4
7 vendors · 9 products
References
19 links
www.debian.org/security/2020/dsa-4751Vendor AdvisoryX Refsource DEBIANMailing ListThird Party Advisory- lists.opensuse.org/opensuse-security-announce/2020-09/msg00012.htmlVendor AdvisoryX Refsource SUSEMailing ListThird Party Advisory
- lists.opensuse.org/opensuse-security-announce/2020-09/msg00017.htmlVendor AdvisoryX Refsource SUSEMailing ListThird Party Advisory
- lists.debian.org/debian-lts-announce/2020/10/msg00005.htmlMailing ListX Refsource MLISTThird Party Advisory