Security readout for executives and security teams
Plain-English summary
This flaw lets a tampered certified PDF appear as though its certification is still valid after content changes. The victim must open the file, so the main business risk is trust failure in PDF-based approvals, contracts, forms, or records rather than system takeover.
Executive priority
Treat as a moderate-priority integrity risk. It is not described as code execution, but it can undermine trust in certified documents. Patch exposed Reader installations and review high-value PDF approval workflows first.
Technical view
CVE-2021-28546 is a CWE-353 missing integrity check in Adobe Acrobat Reader DC. A remote unauthenticated attacker could modify certified PDF content without invalidating certification. CVSS 3.1 is 6.5 with high integrity impact, no confidentiality or availability impact, and required user interaction.
Likely exposure
Exposure is likely on endpoints running Adobe Acrobat Reader DC 2020.013.20074 or earlier, 2020.001.30018 or earlier, or 2017.011.30188 or earlier, especially where certified PDFs are trusted for approvals, compliance, legal, or financial workflows.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. Exploitation requires social delivery of a tampered PDF and a user opening it. The practical risk depends on whether users rely on PDF certification indicators for business decisions.
Researcher notes
The key security property affected is document integrity validation, not host compromise. Evidence supports user-assisted tampered-document abuse only. No exploit status, fixed version details, or broader Adobe product impact should be inferred beyond the supplied CVE and Adobe advisory reference.
Mitigation direction
- Apply Adobe guidance and security updates from APSB21-09.
- Upgrade Acrobat Reader DC beyond the affected version lines.
- Prioritize systems handling signed, certified, legal, or approval PDFs.
- Warn users not to trust unexpected certified PDFs without source verification.
- Review workflows that rely solely on PDF certification indicators.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Compare installed versions against the affected version thresholds.
- Confirm patch status against Adobe APSB21-09 guidance.
- Identify business processes that rely on certified PDF integrity.
- Check email and document gateways for certified PDF handling policy.
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
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CWE-353: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-28546 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
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/acrobat/apsb21-09.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.
Missing Support for Integrity Check
Missing Support for Integrity Check represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.