Security readout for executives and security teams
Plain-English summary
CVE-2021-28565 affects Adobe Acrobat Reader and can be triggered when a user opens a malicious PDF. The bundle describes an out-of-bounds read in PDFLibTool, with potential information exposure and user-context impact. There is no KEV listing or source-provided evidence of active exploitation.
Executive priority
Treat this as a moderate endpoint risk. It needs routine but timely remediation because exploitation depends on user file opening, not direct remote access, and no active exploitation evidence is provided in the bundle.
Technical view
The vulnerability is CWE-125 out-of-bounds read in Acrobat Reader DC 2021.001.20150 and earlier, 2020.001.30020 and earlier, and 2017.011.30194 and earlier. It is unauthenticated, network-origin, low complexity, and requires user interaction. The CVSS vector indicates low confidentiality impact only.
Likely exposure
Exposure is most likely on endpoints running affected Adobe Acrobat Reader DC builds, especially where users open PDFs from email, web downloads, shared drives, or external parties. The source bundle does not identify server-side exposure or non-Reader products.
Exploitation context
The source bundle states exploitation requires a victim to open a malicious file. It does not provide exploit maturity details, and KEV is false, so active exploitation should not be assumed from the available evidence.
Researcher notes
The bundle has a notable inconsistency: the description mentions arbitrary code execution, while the title and CVSS vector indicate out-of-bounds read with low confidentiality impact only. Base conclusions on the cited advisory and CVSS until vendor details are reviewed.
Mitigation direction
- Review Adobe APSB21-29 and apply the vendor-provided Acrobat Reader security update.
- Inventory Acrobat Reader DC versions against the listed affected build thresholds.
- Prioritize patching users who routinely handle external PDFs.
- Maintain email and web controls for suspicious PDF attachments and downloads.
Validation and detection
- Confirm installed Acrobat Reader versions are newer than affected builds listed in the bundle.
- Check endpoint management records for remaining vulnerable Reader installations.
- Verify Adobe update deployment status on high-risk user groups.
- Review security telemetry for suspicious PDF-open events where available.
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-125: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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 lookupCVE-2021-28565 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 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/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:L/I:N/A:N2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/acrobat/apsb21-29.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.
Out-of-bounds Read
Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.