CVE-2026-34621
CVE-2026-34621 is a security flaw in Adobe Acrobat and Reader, Adobe’s software for opening and editing PDFs. Opening a booby-trapped file can let an attacker run their own code through Adobe Acrobat and Reader. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 13 Apr 2026.[1]
Adobe Acrobat and Reader is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Adobe has published a fix or advice.
Description
CISA calls it a prototype pollution in Adobe Acrobat and Reader. In its words: “Adobe Acrobat and Reader contain a prototype pollution vulnerability that allows for arbitrary code execution.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is prototype pollution (CWE-1321), in MITRE’s list of common software weaknesses.
It scores 8.6 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Adobe’s advisory has them[3]. CISA names the product as Adobe Acrobat and Reader.
Every device with Adobe Acrobat and Reader needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 13 Apr 2026, 2 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 27 Apr 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 7%. That’s in the top 6% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Adobe has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.”[1]
- Update Adobe Acrobat and Reader now.Install the latest update from Adobe on every device that has it, and restart when asked. Then turn on automatic updates, so the next fix arrives on its own.
- If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.6.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 7%.[4] |
See also
Other Adobe Acrobat and Reader flaws
- CVE-2009-3459: heap-based buffer overflow ·
- CVE-2023-21608: use-after-free ·
- CVE-2023-26369: out-of-bounds write ·
- CVE-2018-4990: double free ·
- CVE-2010-2883: stack-based buffer overflow ·
- CVE-2009-4324: use-after-free ·
Other Adobe flaws
- CVE-2026-48356, Adobe Commerce and Magento: unrestricted upload of file with dangerous type ·
- CVE-2026-71362, Adobe Commerce and Magento: incorrect authorization ·
- CVE-2026-75650, Adobe Commerce and Magento: improper neutralization of special elements used in a template engine ·
- CVE-2026-48282, Adobe ColdFusion: path traversal ·
- CVE-2020-9715, Adobe Acrobat: use-after-free ·
Added the same day
- CVE-2026-21643, Fortinet FortiClient EMS: SQL injection ·
- CVE-2025-60710, Microsoft Windows: link following ·
- CVE-2023-36424, Microsoft Windows: out-of-bounds read ·
- CVE-2023-21529, Microsoft Exchange Server: deserialization of untrusted data ·
- CVE-2020-9715, Adobe Acrobat: use-after-free ·
Every Adobe flaw on CISA’s list · Everything added in April 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Adobe Acrobat and Reader Prototype Pollution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 13 Apr 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-34621 Detail”. National Vulnerability Database, published 11 Apr 2026.
- ^ Adobe. Advisories and fixes: helpx.adobe.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.072, percentile 94.3, 31 Oct 2026.
- CVE Program. “CVE-2026-34621”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.