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CVE Record

CVE-2021-42204: An issue was discovered in swftools through 20201222.

An issue was discovered in swftools through 20201222. A heap-buffer-overflow exists in the function swf_GetBits() located in rfxswf.c. It allows an attacker to cause code execution.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

SWFTools through 20201222 has a heap buffer overflow in SWF bit parsing. If a vulnerable tool processes a malicious SWF file, the source says an attacker could cause code execution. Business urgency is highest where legacy Flash/SWF processing is exposed to external content. The provided sources do not show active exploitation or a named fix.

Executive priority

Treat this as high priority only where SWFTools handles external or semi-trusted files. If SWFTools is absent or used only on trusted internal inputs, urgency is lower. The key decision is whether any business workflow still processes SWF content with this legacy tool.

Technical view

CVE-2021-42204 identifies a heap-buffer-overflow in swf_GetBits() in rfxswf.c in SWFTools through 20201222. The CVE description says this can allow code execution. The record provides no CVSS, CWE, CPE, patch version, or mitigation details in the supplied bundle.

Likely exposure

Likely exposure is limited to environments that still install or embed SWFTools, especially automated conversion, extraction, or publishing workflows that process SWF files. Public-facing upload handlers, content pipelines, and forensic/media tooling are higher concern if they pass untrusted SWF content to SWFTools.

Exploitation context

The source bundle includes no KEV listing and no cited evidence of active exploitation. The vulnerable condition is file-processing based: risk depends on an attacker getting a crafted SWF file processed by SWFTools. Do not assume internet-wide exploitation from the provided evidence.

Researcher notes

Evidence is sparse. The CVE states heap-buffer-overflow, function name, source file, version boundary, and code execution impact, but omits scoring, weakness classification, affected CPEs, and remediation. Further validation should focus on confirming reachability in local SWFTools invocation paths without relying on exploit reproduction.

Mitigation direction

  • Inventory systems and containers for SWFTools usage.
  • Stop processing untrusted SWF files with vulnerable SWFTools builds.
  • Check the upstream GitHub issue and vendor guidance for fixes.
  • Run SWFTools workloads with least privilege and isolation.
  • Restrict upload or ingestion paths that accept SWF content.

Validation and detection

  • Confirm whether SWFTools is installed in production and build images.
  • Identify workflows that invoke SWFTools on user-supplied files.
  • Record installed SWFTools version and build date.
  • Review upload, conversion, and archive-processing paths for SWF handling.
  • Monitor vendor issue references for patch or mitigation updates.
Prepared
Confidence
medium
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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Execution behavior lookup

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CVE-2021-42204 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

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.

0CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.