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CVE Record

CVE-2021-24002: When a user clicked on an FTP URL containing encoded newline characters (%0A and %0D), the newlines would h...

When a user clicked on an FTP URL containing encoded newline characters (%0A and %0D), the newlines would have been interpreted as such and allowed arbitrary commands to be sent to the FTP server. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

A crafted FTP link could make vulnerable Mozilla clients send unintended commands to an FTP server when a user clicked it. The evidence identifies affected Firefox, Firefox ESR, and Thunderbird versions, but provides no CVSS score or confirmed exploitation. This is primarily a client-update and exposure-management issue.

Executive priority

Treat this as a routine but necessary legacy-client remediation item. It does not have confirmed active exploitation in the provided sources, but vulnerable versions are old and should be removed from managed environments.

Technical view

The flaw is newline handling in FTP URLs: encoded carriage return or line feed characters were interpreted as real newlines, allowing arbitrary FTP commands to be sent to the server. Affected versions are Firefox before 88, Firefox ESR before 78.10, and Thunderbird before 78.10.

Likely exposure

Exposure is most likely on endpoints running older Mozilla Firefox, Firefox ESR, or Thunderbird builds, especially where users can click FTP links from web pages, email, or documents. Supported, updated clients should not fall within the listed affected ranges.

Exploitation context

The provided bundle does not show CISA KEV listing or active exploitation. Exploitation would require a user interaction with a crafted FTP URL and would affect commands sent to an FTP server, not directly imply host compromise from the cited text.

Researcher notes

Evidence is limited to public CVE and Mozilla references. No CVSS vector, CWE, proof of exploitation, or detailed vendor mitigation beyond fixed version boundaries is included in the provided bundle. Avoid assuming broader command execution or server impact beyond FTP commands sent by the client.

Mitigation direction

  • Upgrade Firefox to version 88 or later.
  • Upgrade Firefox ESR to version 78.10 or later.
  • Upgrade Thunderbird to version 78.10 or later.
  • Check Mozilla advisory guidance for supported-version remediation details.
  • Prioritize removal of unsupported Mozilla client versions.

Validation and detection

  • Inventory installed Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Flag Firefox versions earlier than 88.
  • Flag Firefox ESR and Thunderbird versions earlier than 78.10.
  • Review email and browser policy controls for FTP URL exposure.
  • Confirm updates through endpoint management or software inventory reports.
Prepared
Confidence
high
Sources
6

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

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CVE-2021-24002 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox ESRunspecifiedListed
MozillaThunderbirdunspecifiedListed
MozillaFirefoxunspecifiedListed
Weakness

CWE details

No CWE listed

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