Security readout for executives and security teams
Plain-English summary
CVE-2021-39556 is a denial-of-service issue in swftools through 20200710. A crafted input can trigger a crash through a NULL pointer dereference. The sources do not provide a CVSS score, confirmed fixed version, or evidence of active exploitation.
Executive priority
Prioritize if swftools is used in customer-facing or automated file-processing workflows, because crashes can disrupt service. If swftools is absent or only used on trusted internal inputs, urgency is lower but inventory should still be completed.
Technical view
The issue is reported in InfoOutputDev::type3D1() in InfoOutputDev.cc. The flaw is a NULL pointer dereference that allows denial of service. Affected scope is only stated as swftools through 20200710; product CPEs and CWE data are not provided in the source bundle.
Likely exposure
Exposure is most likely where swftools through 20200710 processes untrusted or user-supplied files. The provided CVE record does not identify packaged distributions, CPEs, deployment types, or a fixed version.
Exploitation context
The CVE is not listed as KEV in the source bundle. The provided sources do not state active exploitation, exploit availability, or observed attacks. Treat exploitation status as unconfirmed.
Researcher notes
Evidence is sparse: no CVSS, CWE, CPE, patch version, or exploit status is supplied. The strongest source-grounded finding is a NULL pointer dereference in InfoOutputDev::type3D1() causing denial of service in swftools through 20200710.
Mitigation direction
- Inventory systems and pipelines that use swftools through 20200710.
- Check upstream swftools guidance and issue #105 for fixes or safe versions.
- Avoid processing untrusted files with affected swftools builds until remediation is confirmed.
- If continued use is required, isolate processing to limit denial-of-service impact.
Validation and detection
- Confirm installed swftools versions across servers, build images, and processing jobs.
- Identify workflows where swftools handles external or user-supplied input.
- Review upstream issue #105 and CVE records for any remediation updates.
- Monitor service crash logs around swftools execution paths.
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-2021-39556 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/105CVE 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.