CVE-2021-39853

Application crash via malicious-file null dereference

Published Sep 29, 2021 · Updated Sep 17, 2024

NULL pointer dereference in Adobe Acrobat Reader DC 2021.005.20060 and earlier allows attackers to crash the application via a malicious file. Adobe has not disclosed the affected parser or the operation that dereferences the null pointer while processing the file. Reader 2020 2020.004.30006 and earlier and Reader 2017 2017.011.30199 and earlier are also affected; a victim must open the file, and the consequence is limited to crashing the current user's application.

CVSS severity5.5
Medium
EPSS probability2.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Adobe Acrobat Reader DC 2021.005.20060 and earlier allows attackers to crash the application via a malicious file. Adobe has not disclosed the affected parser or the operation that dereferences the null pointer while processing the file. Reader 2020 2020.004.30006 and earlier and Reader 2017 2017.011.30199 and earlier are also affected; a victim must open the file, and the consequence is limited to crashing the current user's application.

The record

CVE
CVE-2021-39853
Published
Sep 29, 2021
Updated
Sep 17, 2024
Vendor
Adobe
Product
Adobe Acrobat Reader
Classifications
CWE-476, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <=17.0-Classic 2021 July
  2. Affected versionversion=unspecified <=20.0-Classic 2021 July
  3. Affected versionversion=unspecified <=DC 2021 July
  4. Affected versionversion=unspecified <=None

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Adobe · Adobe Acrobat Readerversion=unspecified <=17.0-Classic 2021 July; version=unspecified <=20.0-Classic 2021 July; version=unspecified <=DC 2021 July; version=unspecified <=None

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
5.5Adobe Systems IncorporatedCVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1204.002User Execution: Malicious File

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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