dbcve.org
LibredwgApplication · Gnu

CVE-2020-21816

HIGH · 8.8 CVSS v3.1 Published 2021-05-17
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
95/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A heab based buffer overflow issue exists in GNU LibreDWG 0.10.2641 via htmlescape ../../programs/escape.c:46.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A heap-based buffer overflow vulnerability exists in the htmlescape function in GNU LibreDWG version 0.10.2641 (and possibly earlier versions). The overflow occurs in programs/escape.c at line 46, where insufficient bounds checking during HTML escaping allows a remote attacker to overflow a heap-allocated buffer, potentially leading to denial of service or arbitrary code execution.

MitigationUpdate GNU LibreDWG to the latest patched version. If no update is available, implement input length validation and proper buffer size checking in the htmlescape function before processing any data.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
LibredwgApplication
Affected:= 0.10.2641

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify GNU LibreDWG installation
    Run 'dpkg -l libredwg' on Debian-based systems, 'rpm -qa | grep -i redwg' on RHEL-based systems, or check for the 'dwggrep' or 'dwg2dxf' binaries in your PATH using 'which dwggrep' or 'which dwg2dxf'
    Affected if LibreDWG is not installed or no binaries are found in PATH
  2. Check installed LibreDWG version
    Run 'libredwg --version' or check the package version via your system's package manager. Compare the version number to 0.10.2641 or earlier versions.
    Affected if The installed version is 0.10.2641 or any version prior to it
  3. Identify processes or tools using the htmlescape function
    Search for compiled binaries or scripts that link against the LibreDWG library and invoke HTML escaping functionality. Review application logs or code that calls escape.c functions.
    Affected if Any tool or application uses LibreDWG's escape functionality for HTML processing
  4. Inspect the escape.c file in your LibreDWG installation
    Locate the programs/escape.c file in your installed LibreDWG source or package (typically in /usr/src or /usr/share/libredwg). Verify line 46 contains the htmlescape function with bounds checking logic.
    Affected if The escape.c file exists and contains the vulnerable htmlescape function at line 46
  5. Test htmlescape with oversized input
    If you have access to the htmlescape function via CLI tool or test harness, provide an HTML string exceeding typical buffer limits to observe for crashes or memory corruption indicators.
    Affected if The program crashes, aborts, or exhibits undefined behavior when processing large HTML strings

You are affected if GNU LibreDWG version 0.10.2641 or earlier is installed AND your environment uses the htmlescape function for HTML escaping operations.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch github.com →
Interim mitigation

Update GNU LibreDWG to the latest patched version. If no update is available, implement input length validation and proper buffer size checking in the htmlescape function before processing any data.

Recommended fix Moderate confidence

Latest stable release beyond 0.10.2641 (check GitHub releases for post-0.10.2641 version)

  1. 1. Identify all systems running Libredwg version 0.10.2641
  2. 2. Upgrade Libredwg to the latest stable version available from the official repository at https://github.com/LibreDWG/libredwg
  3. 3. Verify the upgrade by checking the installed version: `libredwg --version`
  4. 4. Test that affected functionality (htmlescape in programs/escape.c) works correctly with the new version
  5. 5. Re-scan or re-test for the presence of CVE-2020-21816 to confirm remediation
Caveat Review release notes for any breaking changes between 0.10.2641 and the target version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Libredwg Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
Get the patch applied

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-21816 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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