CVE-2023-21608
CVE-2023-21608 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 10 Oct 2023.[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 an use-after-free in Adobe Acrobat and Reader. In its words: “Adobe Acrobat and Reader contains a use-after-free vulnerability that allows for code execution in the context of the current user.”[1]
The CVE record adds: “Adobe Acrobat Reader versions 22.003.20282 (and earlier), 22.003.20281 (and earlier) and 20.005.30418 (and earlier) are affected by a Use After Free 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 use after free (CWE-416), in MITRE’s list of common software weaknesses.
It scores 7.8 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 10 Oct 2023, 265 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 31 Oct 2023 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 59%. That’s in the top 1% 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 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 7.8.[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 59%.[4] |
See also
Other Adobe Acrobat and Reader flaws
- CVE-2009-3459: heap-based buffer overflow ·
- CVE-2026-34621: prototype pollution ·
- 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 ·
Other use after free flaws
- CVE-2026-109619, PHP: stale internal request-state ·
- CVE-2026-109618, PHP: memory corruption ·
- CVE-2026-68820, Microsoft Windows Ancillary Function Driver for WinSock: use-after-free ·
- CVE-2010-0249, Microsoft Internet Explorer: use-after-free ·
- CVE-2026-5281, Google Dawn: use-after-free ·
Added the same day
- CVE-2023-44487, IETF HTTP/2: rapid reset attack ·
- CVE-2023-41763, Microsoft Skype for Business: privilege escalation ·
- CVE-2023-36563, Microsoft WordPad: information disclosure ·
- CVE-2023-20109, Cisco IOS and IOS XE: group encrypted transport VPN out-of-bounds write ·
Every Adobe flaw on CISA’s list · Everything added in October 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Adobe Acrobat and Reader Use-After-Free Vulnerability”. Known Exploited Vulnerabilities Catalog, added 10 Oct 2023.
- ^ National Institute of Standards and Technology. “CVE-2023-21608 Detail”. National Vulnerability Database, published 18 Jan 2023.
- ^ Adobe. Advisories and fixes: helpx.adobe.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.594, percentile 99.1, 31 Oct 2026.
- CVE Program. “CVE-2023-21608”. 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.