CVE-2021-39842 | Adobe Acrobat Reader DC messageHandler.OnMessage Use-After-Free Vulnerability

Acrobat Reader DC versions 2021.005.20060 (and earlier), 2020.004.30006 (and earlier) and 2017.011.30199 (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.

Published: 2021-09-29 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-39842 is rated Moderate Risk (60/100): CVSS High severity, with high exploitation likelihood (EPSS 16.83%, 97th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-39842

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 45.46% 16.83% -28.63%
2 2026-04-17 50.75% 45.46% -5.29%
3 2026-02-02 — 50.75% —

Full EPSS history (39 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-39842

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.8 3.0 HIGH
CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2021-39842

Affected software / configurations for CVE-2021-39842

Vendor Product Version Raw CPE
adobe acrobat >= 20.001.30005, <= 20.004.30006 cpe:2.3:a:adobe:acrobat:*:*:*:*:classic:*:*:*
adobe acrobat_reader >= 20.001.30005, <= 20.004.30006 cpe:2.3:a:adobe:acrobat_reader:*:*:*:*:classic:*:*:*
adobe acrobat_dc >= 15.008.20082, <= 21.005.20058 cpe:2.3:a:adobe:acrobat_dc:*:*:*:*:continuous:*:*:*
adobe acrobat_reader_dc >= 15.008.20082, <= 21.005.20058 cpe:2.3:a:adobe:acrobat_reader_dc:*:*:*:*:continuous:*:*:*
adobe acrobat_dc >= 15.008.20082, <= 21.005.20060 cpe:2.3:a:adobe:acrobat_dc:*:*:*:*:continuous:*:*:*
adobe acrobat_reader_dc >= 15.008.20082, <= 21.005.20060 cpe:2.3:a:adobe:acrobat_reader_dc:*:*:*:*:continuous:*:*:*
adobe acrobat >= 17.011.30059, <= 17.011.30199 cpe:2.3:a:adobe:acrobat:*:*:*:*:classic:*:*:*
adobe acrobat_reader >= 17.011.30059, <= 17.011.30199 cpe:2.3:a:adobe:acrobat_reader:*:*:*:*:classic:*:*:*

References for CVE-2021-39842

cvelogic Threat Intelligence