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CVE Record

CVE-2021-47839: Marky 0.0.1 - Persistent Cross-Site Scripting

Marky 0.0.1 contains a persistent cross-site scripting vulnerability that allows attackers to inject malicious scripts into markdown files. Attackers can upload crafted markdown files with embedded JavaScript payloads that execute when the file is opened, potentially enabling remote code execution.

HighCVSS 7.2Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Marky 0.0.1 is reported to store unsafe JavaScript inside markdown files. If an organization uses this tool with untrusted markdown, a malicious file could run script when rendered or opened. The sources include public exploit references, but the bundle does not show known active exploitation or a named vendor patch.

Executive priority

Prioritize inventory and containment where Marky handles external markdown. This is high severity but likely narrow in footprint. Escalate only if Marky 0.0.1 is internet-facing, multi-user, or used with customer-supplied content.

Technical view

CVE-2021-47839 is a CWE-79 persistent cross-site scripting issue in vesparny Marky 0.0.1. The bundle says crafted markdown can embed JavaScript that executes when the file is opened. CVSS is 7.2 high. Evidence also claims possible remote code execution, but the provided details do not explain that impact chain.

Likely exposure

Exposure appears limited to deployments or workflows using vesparny Marky 0.0.1, especially where users can upload or open untrusted markdown. Organizations not using Marky, or not accepting untrusted markdown into it, are unlikely to be exposed based on this bundle.

Exploitation context

The CVE is not listed as KEV in the supplied data. Public exploit and proof-of-concept references are cited, so defenders should treat reproduction as publicly documented. Do not infer active exploitation from those references alone.

Researcher notes

The source bundle contains public exploit references but limited primary technical detail. The CVSS vector lists no user interaction, while the description says execution occurs when a file is opened. Treat impact beyond persistent XSS as unproven unless confirmed by vendor or advisory detail.

Mitigation direction

  • Inventory Marky usage and confirm whether version 0.0.1 is deployed.
  • Avoid opening or importing untrusted markdown in affected Marky workflows.
  • Restrict markdown upload or edit access to trusted users only.
  • Check upstream Marky and advisory sources for fixed versions or official guidance.
  • Retire or isolate affected workflows if no vendor fix is available.

Validation and detection

  • Search asset and dependency inventories for vesparny Marky 0.0.1.
  • Review applications that render uploaded markdown through Marky.
  • Confirm whether markdown content can be supplied by anonymous or external users.
  • Inspect stored markdown repositories for unexpected embedded script content.
  • Track CVE, VulnCheck, Red Hat, and upstream repository updates.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-79: User-session and phishing behavior lookup

Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-47839 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.2 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
8Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.2CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N3.92.7VulnCheck
5.1CVSS 4.0MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N——VulnCheck

Vulnerability scoring details

Base CVSS 4.0 score

5.1Medium
CVSS 4.0 vector shape for CVE-2021-47839Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPmarky: Marky: Remote Code Execution via persistent cross-site scripting
other:Red Hat severity rating
  • 2026-01-16T20:01:50.311Z: Reported to Red Hat.
  • 2026-01-16T19:09:37.915Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
vesparnyMarky0.0.1Listed
Weakness

CWE details

CWE-79

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-79 · source CWE mapping

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs