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NVD / CVE Program· CNA mitre

CVE-2020-21523: A Server-Side Freemarker template injection vulnerability in halo CMS v1.1.3 In the Edit Theme File function.

CriticalCVSS 9.8 · v3.1—No exploit No fix recorded

Noroxi assessment

Priority: Plan (action score 40/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 2.5% (FIRST EPSS); higher than 85.4% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.

Add it to your regular patch cycle. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A Server-Side Freemarker template injection vulnerability in halo CMS v1.1.3 In the Edit Theme File function. The ftl file can be edited. This is the Freemarker template file. This file can cause arbitrary code execution when it is rendered in the background. exp: <#assign test="freemarker.template.utility.Execute"?new()> ${test("touch /tmp/freemarkerPwned")}

Published
Sep 30, 2020
Updated
Jun 16, 2026
EPSS
2.5% · 85th percentile

Report tools

JSON

Action score

40

Plan

Add it to your regular patch cycle.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.5%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

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Follow CVE-2020-21523

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
halohalo

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • halo halo1.1.3

Same product

halo: all records

Other highest-scoring records for the same primary product.

  • CVE-2022-32994Halo CMS v1.5.3 was discovered to contain an arbitrary file upload vulnerability via the component /api/admin/attachments/upload.
    45Plan
  • CVE-2022-32995Halo CMS v1.5.3 was discovered to contain a Server-Side Request Forgery (SSRF) via the template remote download function.
    44Plan
  • CVE-2020-21526An Arbitrary file writing vulnerability in halo v1.1.3.
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2020-19007Aug 26, 2020 · Halo blog 1.2.0 allows users to submit comments on blog posts via /api/content/posts/comments.
    21Monitor
  • ← EarlierCVE-2020-21522Sep 30, 2020 · An issue was discovered in halo V1.1.3.
    39Monitor
  • Later →CVE-2020-21524Sep 30, 2020 · There is a XML external entity (XXE) vulnerability in halo v1.1.3, The function of importing other blogs in the…
    36Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-74 · Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

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