Security readout for executives and security teams
Plain-English summary
CVE-2021-39593 is a denial-of-service issue in swftools through 20200710. A crafted input may trigger a NULL pointer dereference and crash the tool. The business impact is mainly service interruption where swftools processes SWF files automatically or from untrusted sources.
Executive priority
Prioritize where swftools is internet-facing or processes customer-supplied files automatically. Otherwise, handle as legacy tooling cleanup with availability risk, pending vendor guidance.
Technical view
The reported flaw is a NULL pointer dereference in swf_FontExtract_DefineFontInfo() in swftext.c. The CVE description states this can allow an attacker to cause denial of service. The source bundle does not provide CVSS, CWE mapping, patch status, or detailed affected package metadata.
Likely exposure
Exposure is most likely in legacy media conversion, document-processing, security-analysis, or batch pipelines that still invoke swftools on SWF input, especially externally supplied files.
Exploitation context
The bundle does not show CISA KEV listing or other evidence of active exploitation. Public evidence supports denial-of-service potential, but not remote code execution, privilege escalation, or exploitation in the wild.
Researcher notes
Evidence is limited to the CVE description and linked GitHub issue. Validate exposure by locating swftools execution paths and version data; avoid assuming broader product impact beyond swftools through 20200710.
Mitigation direction
- Inventory systems and pipelines that invoke swftools.
- Check upstream and package-maintainer guidance for fixed or supported versions.
- Avoid processing untrusted SWF files with affected swftools builds.
- Remove swftools where SWF processing is no longer required.
- Isolate required SWF processing with least privilege and crash monitoring.
Validation and detection
- Confirm whether installed swftools versions are through 20200710.
- Map all user-controlled paths that can submit SWF input.
- Review service logs for swftools crashes or abnormal exits.
- Check whether SWF processing failures affect customer-facing availability.
- Verify any replacement or upgrade against normal conversion workflows.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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.
CVE-2021-39593 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/matthiaskramm/swftools/issues/139CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.