CVE-2021-28550 | Adobe Acrobat Reader use after free vulnerability could lead to arbitrary code execution

Exp

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.

Published: 2021-09-02 Last update: 2025-10-23 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-28550 is rated Critical Active Threat (89.3/100): CVSS High severity, with high exploitation likelihood (EPSS 30.72%, 97th percentile). CISA KEV confirms active exploitation (added 2021-11-03) affecting Adobe / Acrobat and Reader. a weakness (CWE-416) Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

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

CISA KEV Record for CVE-2021-28550

Name: Adobe Acrobat and Reader Use-After-Free Vulnerability · CISA KEV detail

Exploit added: 2021-11-03

Action due: 2021-11-17

Required action: Apply updates per vendor instructions.

Exploit prediction scoring system (EPSS) score for CVE-2021-28550

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 2026-05-22 35.47% 30.72% -4.74%
2 2026-05-12 32.57% 35.47% +2.90%
3 2026-04-15 — 32.57% —

Full EPSS history (45 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-28550

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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.
 2.8 5.9 [email protected]
9.6 3.0 CRITICAL
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
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.
 2.8 6.0 [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-2021-28550

OS Trackers for CVE-2021-28550

vendor priority summary link
alpine — CVE-2021-28550: 1 source package rows (tor); 7 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 7, open 0. https://security.alpinelinux.org/vuln/CVE-2021-28550

Affected software / configurations for CVE-2021-28550

Vendor Product Version Raw CPE
adobe acrobat_dc >= 15.008.20082, <= 21.001.20150 cpe:2.3:a:adobe:acrobat_dc:*:*:*:*:continuous:*:*:*
adobe acrobat_reader_dc >= 15.008.20082, <= 21.001.20150 cpe:2.3:a:adobe:acrobat_reader_dc:*:*:*:*:continuous:*:*:*
adobe acrobat >= 17.011.30059, <= 17.011.30194 cpe:2.3:a:adobe:acrobat:*:*:*:*:classic:*:*:*
adobe acrobat >= 20.001.30005, <= 20.001.30020 cpe:2.3:a:adobe:acrobat:*:*:*:*:classic:*:*:*
adobe acrobat_reader >= 17.011.30059, <= 17.011.30194 cpe:2.3:a:adobe:acrobat_reader:*:*:*:*:classic:*:*:*
adobe acrobat_reader >= 20.001.30005, <= 20.001.30020 cpe:2.3:a:adobe:acrobat_reader:*:*:*:*:classic:*:*:*
adobe acrobat_dc >= 15.008.20082, <= 21.001.20149 cpe:2.3:a:adobe:acrobat_dc:*:*:*:*:continuous:*:*:*
adobe acrobat_reader_dc >= 15.008.20082, <= 21.001.20149 cpe:2.3:a:adobe:acrobat_reader_dc:*:*:*:*:continuous:*:*:*

References for CVE-2021-28550

cvelogic Threat Intelligence