CVE-2021-21017

CVE-2021-21017 is a high-severity vulnerability in Adobe Acrobat with a CVSS 3.x base score of 8.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2021-11-03). The underlying weakness is classified as CWE-787.

Key facts

• Severity: High (CVSS 3.x base score 8.8)
• CVSS v2: 6.8
• EPSS exploit prediction: 86% (100th percentile)
• Actively exploited: Yes — listed in CISA KEV (added 2021-11-03)
• EU (EUVD) id: EUVD-2021-8423
• EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2021-11-03)
• Weakness: CWE-787
• Affected product: Adobe Acrobat
• Published: 2021-02-11
• Last modified: 2026-06-17

Description

Acrobat Reader DC versions versions 2020.013.20074 (and earlier), 2020.001.30018 (and earlier) and 2017.011.30188 (and earlier) are affected by a heap-based buffer overflow 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.

Frequently asked questions

What is CVE-2021-21017?

Acrobat Reader DC versions versions 2020.013.20074 (and earlier), 2020.001.30018 (and earlier) and 2017.011.30188 (and earlier) are affected by a heap-based buffer overflow 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.

How severe is CVE-2021-21017?

CVE-2021-21017 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-21017 being actively exploited?

Yes. CVE-2021-21017 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2021-21017?

CVE-2021-21017 primarily affects Adobe Acrobat. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-21017?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2021-21017 have an EU (EUVD) identifier?

Yes. CVE-2021-21017 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-8423. It is also flagged as exploited in the EUVD (since 2021-11-03).

When was CVE-2021-21017 published?

CVE-2021-21017 was published on 2021-02-11 and last updated on 2026-06-17.

References

• https://helpx.adobe.com/security/products/acrobat/apsb21-09.html
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21017

Affected products (4)

• cpe:2.3:a:adobe:acrobat:*:*:*:*:classic:*:*:*
• cpe:2.3:a:adobe:acrobat_dc:*:*:*:*:continuous:*:*:*
• cpe:2.3:a:adobe:acrobat_reader:*:*:*:*:classic:*:*:*
• cpe:2.3:a:adobe:acrobat_reader_dc:*:*:*:*:continuous:*:*:*

More vulnerabilities in Adobe Acrobat

• CVE-2018-4872 — Critical (CVSS 10.0): An issue was discovered in Adobe Acrobat Reader 2018.009.20050 and earlier versions, 2017.011.30070 and earlier…
• CVE-2016-1044 — Critical (CVSS 10.0): Adobe Reader and Acrobat before 11.0.16, Acrobat and Acrobat Reader DC Classic before 15.006.30172, and Acrobat and…
• CVE-2016-1041 — Critical (CVSS 10.0): Adobe Reader and Acrobat before 11.0.16, Acrobat and Acrobat Reader DC Classic before 15.006.30172, and Acrobat and…
• CVE-2016-1038 — Critical (CVSS 10.0): Adobe Reader and Acrobat before 11.0.16, Acrobat and Acrobat Reader DC Classic before 15.006.30172, and Acrobat and…
• CVE-2015-7622 — Critical (CVSS 10.0): Adobe Reader and Acrobat 10.x before 10.1.16 and 11.x before 11.0.13, Acrobat and Acrobat Reader DC Classic before…
• CVE-2015-6691 — Critical (CVSS 10.0): Use-after-free vulnerability in Adobe Reader and Acrobat 10.x before 10.1.16 and 11.x before 11.0.13, Acrobat and…

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