Security readout for executives and security teams
Plain-English summary
CVE-2021-39521 is a denial-of-service issue in LibreDWG/libredwg through v0.10.1.3751. A malformed DWG-related input can trigger a NULL pointer dereference and crash affected processing. The sources do not show data theft, code execution, or confirmed active exploitation.
Executive priority
Treat this as a contained availability risk. Prioritize remediation where DWG parsing is internet-facing, automated, or business-critical. Lower urgency is reasonable for isolated internal use with trusted files only.
Technical view
The vulnerability is a NULL pointer dereference in bit_read_BB() in bits.c, reported against libredwg through v0.10.1.3751. The documented impact is denial of service. The source bundle provides no CVSS score, CWE mapping, proof of active exploitation, or named fixed version.
Likely exposure
Exposure is likely limited to systems embedding LibreDWG/libredwg, especially where DWG files are parsed from untrusted or external sources. The sources do not identify downstream affected products, distributions, or hosted services.
Exploitation context
The CVE states an attacker can cause denial of service. It is not in KEV, and the provided sources do not support claims of active exploitation, remote code execution, privilege escalation, or data compromise.
Researcher notes
Evidence is sparse: the record names bit_read_BB() in bits.c and denial-of-service impact, but does not provide CVSS, CWE, fixed release, or downstream product mapping. Avoid assuming broader impact without local dependency evidence.
Mitigation direction
- Check upstream LibreDWG guidance and releases for a fixed version.
- Avoid processing untrusted DWG files with affected libredwg builds.
- Isolate DWG parsing workloads from critical services where practical.
- Add monitoring for repeated parser crashes or failed DWG processing.
- Apply vendor or distribution updates when available.
Validation and detection
- Inventory systems and applications using LibreDWG/libredwg.
- Confirm whether deployed versions are through v0.10.1.3751.
- Identify workflows that parse DWG files from external users.
- Review crash logs for failures in DWG parsing paths.
- Track the referenced GitHub issue for upstream resolution details.
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-2021-39521 mapping review
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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/LibreDWG/libredwg/issues/262CVE 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.