Security readout for executives and security teams
Plain-English summary
CVE-2021-39553 is a denial-of-service flaw in swftools through 20200710. A malicious or malformed input processed by swftools can trigger a NULL pointer dereference and crash the process. The business risk is service disruption where swftools handles untrusted files.
Executive priority
Treat this as a targeted availability risk. Prioritize systems where swftools processes customer-supplied or internet-sourced files, especially if crashes affect production services or automated document workflows.
Technical view
The CVE describes a NULL pointer dereference in grealloc() in gmem.cc in swftools through 20200710. The stated impact is denial of service. The provided records do not include CVSS, CWE, CPEs, fixed versions, or vendor mitigation details.
Likely exposure
Exposure is most likely where swftools is installed on servers, pipelines, or workstations and processes files from users, customers, email, or other untrusted sources. The provided affected metadata is incomplete and lists no CPEs.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. The available evidence supports crash-based denial of service, not data theft, code execution, or privilege escalation.
Researcher notes
Evidence is sparse. The CVE identifies grealloc() in gmem.cc and a NULL pointer dereference, but the supplied data lacks CVSS, CWE, precise affected package metadata, and fixed-version guidance. Avoid assuming exploit maturity beyond denial of service.
Mitigation direction
- Inventory systems, containers, and build pipelines for swftools usage.
- Avoid processing untrusted SWF-related input with vulnerable swftools versions.
- Isolate file-processing workloads to limit crash impact.
- Check upstream project guidance for any fixed release or patch.
- Replace or retire swftools where no maintained fix is available.
Validation and detection
- Confirm whether swftools is installed or bundled in applications.
- Identify workflows that pass external files into swftools.
- Verify deployed versions against swftools through 20200710.
- Review crash logs for swftools faults in gmem.cc or grealloc().
- Use non-offensive regression testing to confirm file-processing stability.
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-2021-39553 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/103CVE 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.