How severe is CVE-2021-39840?

CVE-2021-39840 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-39840 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 50% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39840?

CVE-2021-39840 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-2021-39840?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-39840 published?

CVE-2021-39840 was published on 2021-09-29 and last updated on 2026-06-17.

CVE-2021-39840

CVE-2021-39840 is a high-severity vulnerability in Adobe Acrobat with a CVSS 3.x base score of 7.8. Its EPSS exploit-prediction score of 50% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-416.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 6.8
EPSS exploit prediction: 50% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-416
Affected product: Adobe Acrobat
Published: 2021-09-29
Last modified: 2026-06-17

Description

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 when processing AcroForms that could result in arbitrary code execution in the context of the current user. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.

Frequently asked questions

What is CVE-2021-39840?: 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 when processing AcroForms that could result in arbitrary code execution in the context of the current user. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
How severe is CVE-2021-39840?: CVE-2021-39840 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-39840 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 50% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39840?: CVE-2021-39840 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-2021-39840?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-39840 published?: CVE-2021-39840 was published on 2021-09-29 and last updated on 2026-06-17.

References

https://helpx.adobe.com/security/products/acrobat/apsb21-55.html

Affected products (4)

cpe:2.3:a:adobe:acrobat:*:*:*:*:classic:*:*:*
cpe:2.3:a:adobe:acrobat_reader:*:*:*:*:classic:*:*:*
cpe:2.3:a:adobe:acrobat_dc:*:*:*:*:continuous:*:*:*
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…

All CVEs affecting Adobe Acrobat →

Other CWE-416 (Use After Free) vulnerabilities

CVE-2026-13782 — Critical (CVSS 10.0): Use after free in Browser in Google Chrome prior to 150.0.7871.47 allowed a remote attacker who had compromised the…
CVE-2026-4725 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149…
CVE-2026-4688 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox…
CVE-2025-24085 — Critical (CVSS 10.0): A use after free issue was addressed with improved memory management. This issue is fixed in iOS 18.3 and iPadOS 18.3,…
CVE-2024-43102 — Critical (CVSS 10.0): Concurrent removals of certain anonymous shared memory mappings by using the UMTX_SHM_DESTROY sub-request of…
CVE-2021-32495 — Critical (CVSS 10.0): Radare2 has a use-after-free vulnerability in pyc parser's get_none_object function. Attacker can read freed memory…

Browse all CWE-416 (Use After Free) vulnerabilities →