Security readout for executives and security teams
Plain-English summary
CVE-2021-1252 can make affected ClamAV scanners hang when processing a specially crafted Excel file. The business impact is availability: malware scanning, email gateways, or file-upload pipelines using vulnerable ClamAV versions may stall or backlog, reducing protection and disrupting dependent workflows.
Executive priority
Treat this as a high-priority availability risk for systems that depend on ClamAV scanning. It is not described as data theft or code execution, but scanner outages can weaken defenses and disrupt business workflows.
Technical view
The flaw is in ClamAV's Excel XLM macro parser in versions 0.103.0 and 0.103.1. Improper error handling can lead to an infinite loop. The CVSS 3.1 score is 7.5, with network attack vector, low complexity, no privileges, no user interaction, and high availability impact.
Likely exposure
Exposure is most likely where ClamAV 0.103.0 or 0.103.1 scans untrusted Excel files, such as mail attachments, web uploads, shared-file repositories, or automated malware-scanning services.
Exploitation context
The bundle does not show CISA KEV listing or cited evidence of active exploitation. Sources state an unauthenticated remote attacker could send a crafted Excel file that makes the ClamAV scanning process hang, causing denial of service.
Researcher notes
Focus validation on version detection and affected file-ingestion paths. Evidence is limited to the CVE data and vendor advisory reference; do not assume broader affected versions, active exploitation, or additional exploitability beyond the documented denial of service.
Mitigation direction
- Inventory ClamAV deployments and identify versions 0.103.0 and 0.103.1.
- Apply the vendor security patch release, ClamAV 0.103.2, or later vendor-supported guidance.
- Prioritize scanners handling email attachments, file uploads, or other untrusted Excel files.
- Monitor scanner health, queue depth, and process hangs until patched.
- Review vendor advisory details before applying compensating controls.
Validation and detection
- Confirm installed ClamAV versions across hosts, containers, and bundled appliances.
- Verify patched systems no longer report ClamAV 0.103.0 or 0.103.1.
- Check security-scanning queues for unusual backlogs or hung processes.
- Confirm mail and upload pipelines still fail closed or alert on scanner unavailability.
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-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-1252 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
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://blog.clamav.net/2021/04/clamav-01032-security-patch-release.htmlCVE reference · vendor-advisory, x_refsource_CISCO
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 Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.