How severe is CVE-2021-28550?

No CVSS score has been assigned to CVE-2021-28550 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2021-28550?

Affected package information for CVE-2021-28550 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-28550?

No fixed release is recorded for CVE-2021-28550 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

How do I detect CVE-2021-28550 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2021-28550 if there is no patch (or I can't update yet)?

Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Is CVE-2021-28550 actively exploited in the wild?

Yes. There are 2 known exploit references for CVE-2021-28550, including 2 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-28550?

CVE-2021-28550 has an EPSS (Exploit Prediction Scoring System) score of 51.9%, placing it in the 99th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2021-28550 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-28550 (Adobe Acrobat and Reader Use-After-Free Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03. CISA required all US federal civilian agencies to remediate this vulnerability by 2021-11-17. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-28550?

CVE-2021-28550 is classified as Use After Free (CWE-416). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-28550 published, and has it been updated?

CVE-2021-28550 was published on September 2, 2021 and was last updated on October 21, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV · ACTIVELY EXPLOITED

CVE-2021-28550

CVE-2021-28550 is a Use After Free vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

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…

Published

Sep 2, 2021

Updated

Oct 21, 2025

Affected

4 products

Patched

See advisory

Exploits

2 known

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2021-11-03. Federal agencies were required to remediate by 2021-11-17.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-28550.

EPSS Exploitation Probability

via FIRST.org ↗

51.9%probability of exploitation in next 30 days

High Risk-0.15%

Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Description

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.

Affected Products

4 products · 8 configurations

Application

acrobatadobe

≥ 20.001.30005 && ≤ 20.001.30020

range

Application

acrobat dcadobe

≥ 15.008.20082 && ≤ 21.001.20149

range

Application

acrobat readeradobe

≥ 20.001.30005 && ≤ 20.001.30020

range

Application

acrobat reader dcadobe

≥ 15.008.20082 && ≤ 21.001.20149

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Acrobat Reader DC versions versions 2021.001.20150 (and earlier), 2020.0…

helpx.adobe.comGoogle-sheetMay 2021

Acrobat Reader DC versions versions 2021.001.20150 (and earlier), 2020.0…

cisa.govCISANov 2021

Detection & mitigation playbook

Vulnerability

Detect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2021-28550 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

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CVE-2021-28550

Exploitation Status

Actively exploited in the wild

EPSS Exploitation Probability

Description

Affected Products

Detection & mitigation playbook

Detect

Remediation status

Mitigate without a patch

Frequently Asked Questions

Is CVE-2021-28550 in your dependencies?