Security readout for executives and security teams
Plain-English summary
SharpZipLib could allow a crafted archive extraction to write a file just outside the intended destination directory. The impact is limited by naming constraints, but it can still create unexpected files in some application workflows. Version 1.3.3 fixed the issue.
Executive priority
Treat as a moderate remediation item. It is not documented as actively exploited, but archive extraction bugs can affect integrity-sensitive workflows. Patch during the next normal security update cycle, sooner for systems handling customer-supplied archives.
Technical view
CVE-2021-32842 is a CWE-22 path traversal flaw in SharpZipLib/#ziplib versions 1.0.0 before 1.3.3. The destination containment check did not require the base directory to end with a slash, allowing prefix-confusion writes to a sibling path whose name begins with the destination directory name.
Likely exposure
Exposure is most likely in .NET applications using SharpZipLib before 1.3.3 to extract archives, especially where archive contents are user-controlled or processed automatically. The source describes limited arbitrary file creation, not full arbitrary path write.
Exploitation context
The bundle has no KEV listing and no cited evidence of active exploitation. CVSS 3.1 score is 4.0 with local attack vector and low integrity impact. Real risk depends on how the application chooses extraction paths and handles archive input.
Researcher notes
The key condition is a non-slash-terminated base directory in containment logic. The described write is constrained to paths that begin like the destination directory one level up, so assess impact against each product’s extraction directory, permissions, and post-extraction behavior.
Mitigation direction
- Upgrade SharpZipLib to version 1.3.3 or later.
- Identify applications that extract archives using SharpZipLib/#ziplib.
- Prioritize systems processing untrusted or externally supplied archives.
- Review vendor advisory and release notes before deployment.
- Check extraction output locations for unexpected sibling files.
Validation and detection
- Confirm dependency versions are not below SharpZipLib 1.3.3.
- Map all code paths that extract archives with SharpZipLib.
- Verify exposed workflows do not process untrusted archives while unpatched.
- Review application logs or filesystem changes around extraction jobs.
- Document compensating controls where upgrade timing is delayed.
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-2021-32842 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
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.