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CVE-2019-12520

26
FAUCET Score

CVE-2019-12520 is a high-severity vulnerability in Squid versions through 4.7 and 5, affecting various Canonical and Debian Linux distributions running Squid. It allows an attacker to manipulate Squid's cache by crafting a URL with a specially encoded username, leading to the serving of malicious content instead of legitimate responses. The vulnerability has a CVSS score of 7.5, indicating a high impact on confidentiality with low attack complexity and no user interaction required. While no public exploit code or active exploitation has been observed, and community discussion is minimal, organizations using affected Squid versions should apply available patches to mitigate this risk.

Impacted Technologies

VendorProductVersion(s)CPE
<= 4.7CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
16.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
18.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
3.94%
Probability of exploitation in next 30 days
EPSS Percentile
89.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0394 is in the 81st percentile among its peer group of 51,553 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

github_advisorypatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: squid:4-8030020200828070549.30b713e6
View patch
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: squid

Vendor Advisories (1)

redhatCVE-2019-12520Moderate

squid: Improper input validation in request allows for proxy manipulation

Apr 24, 2020

References

github.com / squid-cache/squid/commits/v4
PatchThird Party Advisory
gitlab.com / jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12520.txt
Third Party Advisory
lists.debian.org / debian-lts-announce/2020/07/msg00009.html
Mailing ListThird Party Advisory
security.netapp.com / advisory/ntap-20210205-0006
Third Party Advisory
usn.ubuntu.com / 4446-1
Third Party Advisory
debian.org / security/2020/dsa-4682
Third Party Advisory
squid-cache.org / Versions/v4
Release NotesVendor Advisory
squid-cache.org / Versions/v4/changesets
Release NotesVendor Advisory