CVE-2026-34621
Adobe Acrobat and Reader Prototype Pollution Vulnerability
Adobe Acrobat and Reader
Acrobat Reader versions 24.001.30356, 26.001.21367 and earlier are affected by an Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability that could result in 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 13 April 2026. US federal agencies were required to remediate it by 27 April 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 7.2%, which is higher than 94.4% 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:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Frequently asked questions
Is CVE-2026-34621 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-34621.
What does CVE-2026-34621 affect?
CVE-2026-34621 affects Adobe Acrobat and Reader. Acrobat Reader versions 24.001.30356, 26.001.21367 and earlier are affected by an Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability that could result in 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-2026-34621?
CVE-2026-34621 is rated HIGH with a CVSS base score of 8.6. EPSS puts the probability of exploitation in the next 30 days at 7.2%, higher than 94.4% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 27 April 2026.
How should organisations respond to CVE-2026-34621?
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.