Security readout for executives and security teams
Plain-English summary
This vulnerability affects older Adobe Acrobat Reader DC versions. A malicious document could make Reader disclose sensitive memory after a user opens the file. The main business concern is that memory disclosure may help attackers defeat protections such as ASLR, increasing risk when users handle untrusted PDFs.
Executive priority
Treat this as a moderate endpoint patching issue. It is not described as actively exploited in the provided sources, but the confidentiality impact is high and could help attackers weaken memory protections after a malicious PDF is opened.
Technical view
CVE-2021-40723 is a CWE-125 out-of-bounds read in Acrobat Reader DC. Affected versions include 2020.013.20074 and earlier, 2020.001.30018 and earlier, and 2017.011.30188 and earlier. CVSS 3.1 is 5.5: local vector, low complexity, no privileges, user interaction required, high confidentiality impact.
Likely exposure
Exposure is likely on user endpoints running affected Acrobat Reader DC versions, especially where staff open PDFs from email, web downloads, or external parties. The source bundle does not indicate server-side exposure or impact to products beyond Acrobat Reader.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation. Exploitation requires user interaction: a victim must open a malicious file. The documented outcome is sensitive memory disclosure, potentially supporting bypass of mitigations such as ASLR.
Researcher notes
Evidence is limited to the CVE record, CVE List data, and Adobe APSB21-09 reference. The bundle names the vulnerability class, affected version thresholds, CVSS vector, and user-interaction requirement, but does not provide exploit details or a standalone mitigation beyond vendor guidance.
Mitigation direction
- Update affected Acrobat Reader DC installations following Adobe APSB21-09 guidance.
- Prioritize users who regularly process external or untrusted PDF files.
- Remove or upgrade versions at or below the affected version thresholds.
- Reinforce controls against opening unsolicited or unexpected PDF attachments.
- Check Adobe guidance for any product-specific fixed versions or deployment notes.
Validation and detection
- Inventory Acrobat Reader DC versions across managed endpoints.
- Flag versions 2020.013.20074, 2020.001.30018, 2017.011.30188, and earlier.
- Confirm remediation status against Adobe APSB21-09.
- Review security telemetry for suspicious PDF delivery to Reader users.
- Verify high-risk user groups received the Reader update.
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-125: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-40723 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
- 5.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/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:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N1.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.5MediumVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/acrobat/apsb21-09.htmlCVE reference · vendor-advisory
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.