Security readout for executives and security teams
Plain-English summary
CVE-2021-39557 is a denial-of-service issue in swftools through 20200710. A crafted input may trigger a crash, interrupting workflows that rely on swftools. The public bundle does not provide CVSS, a confirmed patch, or affected packaged distributions.
Executive priority
Treat this as a moderate availability risk. Prioritize if swftools is exposed through customer uploads or business-critical conversion workflows; otherwise handle through normal vulnerability management.
Technical view
The issue is a NULL pointer dereference in copyString() in gmem.cc. The stated impact is denial of service. Evidence identifies swftools through 20200710, but the bundle does not include CWE, CVSS, affected CPEs, or remediation details.
Likely exposure
Exposure is most likely where swftools processes untrusted or externally supplied files in automated conversion, publishing, or upload workflows. The source bundle does not identify specific vendors, OS packages, or downstream products.
Exploitation context
The CVE is not listed as CISA KEV in the provided bundle. The cited evidence supports denial-of-service potential, not confirmed active exploitation or remote code execution.
Researcher notes
Public evidence is thin: one CVE description and a GitHub issue reference. No CVSS, CWE, patch identifier, exploit status, or product CPEs are provided, so validation should focus on local usage and upstream confirmation.
Mitigation direction
- Inventory systems and pipelines that use swftools.
- Check upstream swftools guidance and issue 97 for remediation status.
- Avoid processing untrusted files with swftools until risk is addressed.
- Isolate conversion jobs to limit service impact from crashes.
- Remove swftools where it is not operationally required.
Validation and detection
- Confirm whether deployed swftools versions are through 20200710.
- Identify workflows that pass external files into swftools.
- Review crash telemetry for swftools failures around copyString or gmem.cc.
- Check package managers and build manifests for bundled swftools.
- Document compensating controls for any continued exposure.
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-2021-39557 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/97CVE 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.