Security readout for executives and security teams
Plain-English summary
CVE-2021-42839 affects Grand Vice info Co. webopac7. A regular authenticated user could upload a malicious script through the file upload function, then execute code on the server. That could let an attacker take control of the system or disrupt service.
Executive priority
Treat this as high priority where affected webopac7 systems are internet-facing or broadly accessible to users. The impact includes potential server compromise and service interruption, but the supplied evidence does not show active exploitation or a named patch.
Technical view
The issue is CWE-434 arbitrary file upload in webopac7 versions 7.1.20160701 and 1.8.20160701. The upload function fails to filter special characters, enabling remote authenticated attackers to upload and execute scripts. CVSS 3.1 is 8.8: network reachable, low complexity, low privileges required, no user interaction.
Likely exposure
Exposure is likely limited to organizations running the named webopac7 versions, especially internet-facing library or catalog systems with general user login access. The source bundle does not identify additional versions, CPEs, deployment types, or hosted service exposure.
Exploitation context
The CVE is not listed as KEV in the supplied bundle, and the cited sources do not state active exploitation. Exploitation would require a valid general user account and network access to the affected upload function.
Researcher notes
Source evidence is concise and centers on improper upload filtering. Avoid assuming unauthenticated reachability, affected versions beyond those listed, or exploit-in-the-wild status. Focus validation on version confirmation, authenticated upload exposure, and evidence of uploaded executable content.
Mitigation direction
- Check Grand Vice or TWCERT guidance for fixed versions or official workarounds.
- Restrict access to webopac7 upload functionality to trusted users where possible.
- Reduce external exposure to affected webopac7 instances until remediation is confirmed.
- Increase monitoring for suspicious uploads and script execution on affected systems.
- Apply any vendor-provided update or configuration change once identified.
Validation and detection
- Inventory webopac7 deployments and confirm whether versions 7.1.20160701 or 1.8.20160701 are present.
- Identify whether general users can access file upload functionality.
- Review recent uploads for unexpected script-like files or unusual special-character filenames.
- Check application and web server logs for suspicious authenticated upload activity.
- Confirm remediation status against vendor or TWCERT advisory information.
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-434: 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program 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-2021-42839 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
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.twcert.org.tw/tw/cp-132-5288-9d546-1.htmlCVE 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.
Unrestricted Upload of File with Dangerous Type
Unrestricted Upload of File with Dangerous Type represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.