Security readout for executives and security teams
Plain-English summary
CVE-2021-39562 is a denial-of-service flaw in swftools through 20200710. If an attacker can make an affected swftools process handle malicious input, the process may crash. The public sources do not name a patch, fixed version, or active exploitation.
Executive priority
Treat this as a targeted availability risk, not a confirmed breach indicator. Prioritize systems where swftools handles external files or supports customer-facing workflows. Business urgency depends on whether a crash can disrupt important services.
Technical view
The issue is a NULL pointer dereference in FileStream::makeSubStream() in Stream.cc. The documented impact is denial of service. The source bundle does not provide CVSS, CWE mapping, detailed trigger conditions, or remediation specifics beyond the affected swftools version range.
Likely exposure
Exposure is most likely where swftools through 20200710 processes files from users, partners, email, web uploads, or automated content pipelines. Internal-only batch use is lower risk but still vulnerable to malformed or untrusted input.
Exploitation context
The bundle says an attacker can cause denial of service, but it does not show active exploitation. The CVE is not listed as KEV in the provided data. No public exploit status is established here.
Researcher notes
Evidence is sparse. The reliable facts are product family, affected range, function name, file location, NULL dereference class, and denial-of-service impact. No CVSS, CWE, patch, exploit proof, or detailed affected CPEs are provided in the bundle.
Mitigation direction
- Check upstream swftools guidance and the linked issue for remediation status.
- Inventory swftools installations and identify versions through 20200710.
- Avoid processing untrusted files with affected swftools where possible.
- Run file-processing jobs with least privilege and crash isolation.
- Monitor affected workflows for crashes or repeated conversion failures.
Validation and detection
- Confirm whether swftools is installed in production, CI, or content pipelines.
- Record installed swftools versions and compare against through 20200710.
- Map whether swftools receives attacker-controlled or partner-supplied files.
- Review service logs for crashes during file processing.
- Track the CVE and GitHub issue for fixed-version information.
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-2021-39562 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/98CVE 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.