CVE-2021-28550
Adobe Acrobat and Reader Use-After-Free Vulnerability
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 status
CISA Known Exploited Vulnerabilities
Listed by CISA on 3 November 2021. US federal agencies were required to remediate it by 17 November 2021.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 51.9%, which is higher than 98.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2021-28550 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2021-28550.
What does CVE-2021-28550 affect?
CVE-2021-28550 affects 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.
How severe is CVE-2021-28550?
CVE-2021-28550 is rated HIGH with a CVSS base score of 8.8. EPSS puts the probability of exploitation in the next 30 days at 51.9%, higher than 98.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 17 November 2021.
How should organisations respond to CVE-2021-28550?
Apply the vendor patch for Adobe Acrobat and Reader as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.