Security readout for executives and security teams
Plain-English summary
SharpZipLib versions 1.3.0 before 1.3.3 can write files outside the intended extraction directory in a limited way. The impact is integrity-focused: an attacker-controlled archive may create a nearby file whose path begins with the destination directory name. Sources identify a patch in version 1.3.3.
Executive priority
Treat this as a moderate dependency remediation item. It is not presented as remotely exploitable by itself, but archive-processing services can face integrity risk if they accept untrusted files. Upgrade affected dependencies and validate exposed upload or import workflows.
Technical view
This is a CWE-22 path traversal issue in SharpZipLib extraction logic. The destination containment check did not require destDir to end with a slash, allowing paths such as a sibling file prefixed with the destination directory string. CVSS is 4.0, with low integrity impact and no confidentiality or availability impact stated.
Likely exposure
Exposure is most likely in .NET applications using SharpZipLib 1.3.0 through versions before 1.3.3 to extract attacker-supplied archives, especially where destination directories are passed without a trailing slash. Applications not using affected extraction paths or untrusted archives are less likely exposed.
Exploitation context
The provided sources and KEV flag do not show active exploitation. Exploitation requires a vulnerable application flow that extracts crafted archive content with the affected SharpZipLib versions. The documented impact is limited arbitrary file creation constrained by filename and destination directory behavior.
Researcher notes
The key condition is a flawed destination containment check where destDir lacks slash termination. The advisory notes impact is limited by filename and destination directory constraints. Do not broaden scope beyond SharpZipLib versions 1.3.0 before 1.3.3 without separate evidence.
Mitigation direction
- Upgrade SharpZipLib to version 1.3.3 or later.
- Check the GitHub Security Lab advisory and vendor release notes.
- Avoid extracting untrusted archives with affected versions until upgraded.
- Review extraction code for destination path handling assumptions.
- Prioritize services that process user-uploaded archives.
Validation and detection
- Inventory SharpZipLib package versions across source, lockfiles, and deployed artifacts.
- Confirm no runtime uses versions 1.3.0 through before 1.3.3.
- Identify features that extract user-supplied Zip, Tar, GZip, or BZip2 content.
- Review whether extraction destinations rely on string-prefix containment checks.
- Verify patched builds are deployed where archive extraction is reachable.
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.
CWE-22: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-32841 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
- Medium
- CVSS
- 4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
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 vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N2.51.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4MediumVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://securitylab.github.com/advisories/GHSL-2021-125-sharpziplib/CVE reference · x_refsource_CONFIRM
- https://github.com/icsharpcode/SharpZipLib/releases/tag/v1.3.3CVE reference · x_refsource_MISC
- https://github.com/icsharpcode/SharpZipLib/commit/5c3b293de5d65b108e7f2cd0ea8f81c1b8273f78CVE 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.
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.