An issue was discovered in Squid through 4.7 and 5. When receiving a request, Squid checks its cache to see if it can serve up a response. It does this by making a MD5 hash of the absolute URL of the request. If found, it servers the request. The absolute URL can include the decoded UserInfo (username and password) for certain protocols. This decoded info is prepended to the domain. This allows an attacker to provide a username that has special characters to delimit the domain, and treat the rest of the URL as a path or query string. An attacker could first make a request to their domain using an encoded username, then when a request for the target domain comes in that decodes to the exact URL, it will serve the attacker's HTML instead of the real HTML. On Squid servers that also act as reverse proxies, this allows an attacker to gain access to features that only reverse proxies can use, such as ESI.
CVE-2019-12520
“—” beside the score: it is equal to NVD's CVSS score.
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 3.9% (90th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Also known asEUVD-2019-4115 (ENISA EUVD) · GHSA-gx26-q49r-m7g8 (GitHub Security Advisories)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHmedium confidence
- EG Risk
- 35EG Risk 35/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity75% × 45%Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation3.9% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability0% × 15%CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 3.9%
- EPSS %ILE
- 90th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
- EG Likelihood
- 3.9% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-28). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
April 15, 2020
Last Modified
November 21, 2024
Advisory Details (5)
Auto-updated Oct 29, 2026[SECURITY] [DLA 2278-1] squid3 security update
https://lists.debian.org/debian-lts-announce/2020/07/msg00009.htmlsquid/CVEs/CVE-2019-12520.txt · master · Jeriko One / Security · GitLab
https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12520.txtVendor Advisories for CVE-2019-12520(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Patch Availability(2)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| ubuntu | squidclient (3.5.12-1ubuntu7.12) @ xenial | 2026-10-29 | ubuntu |
| redhat | squid:4-8030020200828070549.30b713e6 | 2020-11-04 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(6 across 6 ecosystems)
Debian:10(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| squid | 4.6-1, 4.6-1+deb10u1 |
| — |
Debian:11(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| squid | — |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| squid | — |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| squid | — |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| squid | — |
| — |
Debian:9(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| squid3 | 3.5.23-5, 3.5.23-5+deb9u1 |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Additional Vendor Advisories
(1)
Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.
Data Freshness Timeline
(refreshed 11× in last 7d / 41× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 100 of 197 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 97 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-01 16:28 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-31 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-30 16:28 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-29 16:28 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-29 11:26 UTCEG score recompute
- 2026-10-29 11:26 UTCVendor advisory
- 2026-10-29 11:26 UTCGHSA enrichmentGHSA-gx26-q49r-m7g8
- 2026-10-29 10:55 UTCOSV refresh
- 2026-10-28 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-27 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-26 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-25 19:11 UTCEG score recompute
- 2026-10-25 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-24 16:28 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-23 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-22 16:28 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-21 18:35 UTCEG score recompute
- 2026-10-21 18:35 UTCVendor advisory
- 2026-10-21 18:35 UTCGHSA enrichmentGHSA-gx26-q49r-m7g8
- 2026-10-21 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-20 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-20 02:25 UTCOSV refresh
- 2026-10-19 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-18 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-18 09:55 UTCEG score recompute
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- 2026-10-17 16:28 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-16 16:31 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-15 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-14 16:28 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-13 16:27 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-12 20:03 UTCEG score recompute
- 2026-10-12 16:28 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-12 00:27 UTCEG score recompute
- 2026-10-11 13:41 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-10 19:55 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-09 20:03 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-08 16:37 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-07 23:42 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-06 15:12 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-05 17:39 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-10-03 14:21 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-09-30 14:59 UTCEPSS rescoreEPSS 3.9% · 90th percentile
- 2026-09-30 10:09 UTCEG score recompute
- 2026-09-28 13:46 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-27 13:40 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-27 05:15 UTCOSV refresh
- 2026-09-26 15:53 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-26 00:20 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-24 13:59 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-23 13:43 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-21 20:27 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-20 20:10 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-18 19:22 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-17 19:22 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-16 14:04 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-15 03:05 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-13 16:42 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-12 14:56 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-11 14:48 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-08 21:55 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-07 15:57 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-07 14:48 UTCOSV refresh
- 2026-09-06 13:44 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-05 15:24 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-04 13:56 UTCEPSS rescoreEPSS 3.9% · 89th percentile
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- 2026-09-02 14:07 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-09-01 03:32 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-30 19:13 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-30 01:18 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-28 21:36 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-27 14:21 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-26 14:42 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-25 13:45 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-21 23:45 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-20 23:45 UTCOSV refresh
- 2026-08-20 22:51 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-19 17:00 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-18 13:44 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-17 13:43 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-16 14:52 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-16 02:10 UTCEPSS rescoreEPSS 3.8% · 89th percentile
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- 2026-08-13 21:56 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-12 13:47 UTCEPSS rescoreEPSS 3.8% · 89th percentile
- 2026-08-09 13:43 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-08 16:33 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-07 16:23 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-06 13:43 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-05 19:13 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-05 15:11 UTCOSV refresh
- 2026-08-04 15:05 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-04 10:33 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-03 10:31 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-02 02:23 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-08-01 04:12 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-07-30 16:24 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-07-30 01:27 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-07-28 15:32 UTCEPSS rescoreEPSS 3.9% · 89th percentile
- 2026-07-25 14:14 UTCEPSS rescoreEPSS 3.9% · 89th percentile
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownDebian:9:squid3
- CVE-2020-15049EG 9.9EPSS p93CRITICAL
- CVE-2020-11945EG 9.8EPSS p98CRITICAL
- CVE-2019-12519EG 9.8EPSS p94CRITICAL
- CVE-2019-12524EG 9.8EPSS p90CRITICAL
- CVE-2019-12526EG 9.8EPSS p97CRITICAL
- CVE-2019-12525EG 9.8EPSS p98CRITICAL
- CVE-2019-12523EG 9.1EPSS p91CRITICAL
- CVE-2021-31806NVD 6.5EG 9.0EPSS p100CRITICAL
- CVE-2021-33620NVD 6.5EG 8.8EPSS p100HIGH
- CVE-2020-25097EG 8.6EPSS p94HIGH
Same vendor
10 shownredhat:RHSA-2020:4743
- CVE-2019-12524EG 9.8EPSS p90CRITICAL
- CVE-2019-12523EG 9.1EPSS p91CRITICAL
- CVE-2019-18676EG 7.5EPSS p95HIGH
- CVE-2020-15049EG 9.9EPSS p93CRITICAL
- CVE-2019-12526EG 9.8EPSS p97CRITICAL
- CVE-2020-24606EG 8.6EPSS p92HIGH
- CVE-2020-8450NVD 7.3EG 8.6EPSS p99HIGH
- CVE-2019-18679NVD 7.5EG 7.8EPSS p99HIGH
- CVE-2020-14058EG 7.5HIGH
- CVE-2019-12528EG 7.5EPSS p96HIGH
Frequently asked(5)
What is CVE-2019-12520?
When was the CVE record for CVE-2019-12520 published?
Is CVE-2019-12520 actively exploited?
What is the CVSS score of CVE-2019-12520?
How do I remediate CVE-2019-12520?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2019-12520
Is Your Infrastructure Affected by CVE-2019-12520?
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