IRONSMITHINTEL
HIGHCVSS8.8
|
Actively Exploited
|CISA KEV|CVE-2021-28550|Auth: none — unauthenticated|Reboot: required|Manual only

Adobe Acrobat and Reader Use-After-Free Vulnerability

Adobe Acrobat and Reader contains a use-after-free vulnerability that could allow an unauthenticated attacker to achieve code execution in the context of the current user.

Published Sep 2, 2021 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2021-11-17 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Use After Free (CWE-416) vulnerability in Adobe Acrobat and Reader. Acrobat Reader DC versions versions 2021.001.20150 (and earlier), 2020.001.30020 (and earlier) and 2017.011.30194 (and earlier) are affected by a Use After Free vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file. Exploitation requires remote network access, low attack complexity, no authentication required, and user interaction required.

📧

Phishing link

🖼

Malicious file

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Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

Endpoint Administrators
IT Security
Running acrobat dc: 15.008.20082 ≤ v ≤ 21.001.20150, 15.008.20082 ≤ v ≤ 21.001.20149; acrobat reader dc: 15.008.20082 ≤ v ≤ 21.001.20150, 15.008.20082 ≤ v ≤ 21.001.20149; acrobat: 17.011.30059 ≤ v ≤ 17.011.30194, 20.001.30005 ≤ v ≤ 20.001.30020; acrobat reader: 17.011.30059 ≤ v ≤ 17.011.30194, 20.001.30005 ≤ v ≤ 20.001.30020
Real-world incidentsWhat we've seen

CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2021-11-03 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2021-11-17.

How to patch

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

CISA required action: Apply updates per vendor instructions.

References

    1
    Vendor advisory: https://helpx.adobe.com/security/products/acrobat/apsb21-29.html
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2021-28550
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28550
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