CVE-2020-9713: Adobe Acrobat Reader Memory Disclosure Vulnerability

Technical summary

CVE-2020-9713 is classified as an out-of-bounds read vulnerability (CWE-125) in Adobe Acrobat and Reader. The flaw exists in multiple versions across the 2015, 2017, and 2020 product lines. When processing specially crafted PDF content, the affected applications fail to properly validate memory boundaries during read operations. This results in the application reading beyond the allocated buffer, potentially exposing adjacent memory regions. The CVSS 3.1 score of 5.5 (Medium) reflects a local attack vector requiring user interaction, high confidentiality impact, but no integrity or availability impact. The vulnerability resides in the Acrobat DC and Reader DC families and affects both Windows and macOS platforms.

Business impact

Information disclosure vulnerabilities in PDF readers represent a persistent threat to organizations that rely on PDF processing for document workflows. An attacker exploiting this flaw could obtain sensitive information embedded in the victim's process memory, including authentication tokens, personally identifiable information, trade secrets, or other confidential data. The business risk depends on deployment context: organizations handling regulated data (financial records, healthcare documents, classified materials) face higher exposure. The attack requires social engineering or document distribution—attackers would need to deliver a malicious PDF to a targeted user. Failure to patch leaves users vulnerable to opportunistic or targeted attacks leveraging this vector.

Affected systems

Adobe Acrobat DC and Acrobat Reader DC are affected, along with legacy Acrobat 2017 and 2015 product lines. The vulnerability impacts the following versions and earlier: 2020.009.20074 (Acrobat DC 2020), 2020.001.30002 (Reader DC 2020), 2017.011.30171 (Acrobat 2017), and 2015.006.30523 (Acrobat 2015). Both Windows and macOS operating systems are in scope. Organizations running end-of-life versions (2015, 2017) are encouraged to migrate to supported releases; users on 2020 versions should apply security updates immediately.

Exploitability

Exploitation of CVE-2020-9713 requires user interaction—a victim must open a PDF document supplied by the attacker. No network-based or privilege-escalation attack path exists. The vulnerability is not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog, suggesting active exploitation in the wild has not been broadly documented as of the publication date. However, the out-of-bounds read class of vulnerability is well-understood by security researchers, and proof-of-concept code could potentially be developed. Organizations should not rely on KEV status as the sole measure of risk; targeted attacks using custom malicious PDFs remain feasible.

Remediation

Apply the latest security updates for Adobe Acrobat and Reader as soon as practical. Adobe typically releases cumulative updates addressing multiple vulnerabilities. Verify the patch version against Adobe's official security advisory to confirm CVE-2020-9713 is included in the update. For organizations unable to patch immediately, implement compensating controls: restrict PDF document sources to trusted parties, disable unnecessary PDF features in Reader if possible, and educate users on the risks of opening unsolicited documents. Legacy product versions (2015, 2017) are no longer receiving new security updates; migration to a supported Acrobat DC version is the only long-term remediation path.

Patch guidance

Visit Adobe's official security bulletin to identify the specific patched versions for your product line (Acrobat DC 2020, Reader DC, Acrobat 2017, or Acrobat 2015). Update through Adobe's standard update mechanism (Help > Check for Updates) or download the latest release from adobe.com. Verify the installed version post-patch by opening Help > About and comparing against Adobe's advisory. Consider centralizing update management through your endpoint management platform if available. Test patches in a non-production environment first, particularly if PDFs are mission-critical to your workflow, to rule out any unexpected compatibility issues with legacy document formats or third-party integrations.

Detection guidance

Detection of exploitation attempts is challenging because the vulnerability leaves minimal forensic artifacts on disk—memory is read but not written. Focus on behavioral indicators: monitor for anomalous PDF file sources or suspicious deliveries (unsolicited emails with PDF attachments, unusual file-sharing patterns). Endpoint detection and response (EDR) tools may flag unusual memory access patterns by Acrobat processes if sufficiently tuned, though this requires baselining normal behavior. Network detection is ineffective since the attack is local. Encourage users to report unexpected PDF behavior (freezes, crashes, performance degradation) and preserve memory dumps if available for forensic analysis. Most reliable control remains prevention via patching and user awareness.

Why prioritize this

This vulnerability merits near-term patching due to its presence in widely-deployed PDF readers and the sensitivity of data that may be exposed through memory disclosure. While the CVSS score (5.5) is moderate and exploitation requires user interaction, the business impact—potential exposure of credentials, PII, and confidential documents—justifies swift remediation. The absence from the KEV catalog does not lower risk; targeted attacks using custom malicious PDFs are feasible. Organizations should deprioritize legacy Acrobat versions (2015, 2017) in favor of Acrobat DC 2020, which will receive future security updates. For security teams managing large deployments, staging patch rollouts within 30 days is prudent.

Risk score, explained

The CVSS 3.1 score of 5.5 (Medium) reflects the attack vector (local; requires file access), complexity (low; no special conditions), privileges required (none), and user interaction (required). The impact assessment shows high confidentiality (memory disclosure) but no integrity or availability impact. This scoring is appropriate: the vulnerability does not enable code execution, privilege escalation, or denial of service, but the confidentiality breach is substantial if an attacker successfully crafts a malicious PDF and delivers it to a user. Organizations with sensitive document workflows should treat this as higher priority internally than the base score suggests.

Frequently asked questions