CVE-2021-39846

Code execution via crafted PDF stack overflow

Published Sep 29, 2021 · Updated Sep 16, 2024

Stack-based buffer overflow in affected Adobe Acrobat Reader versions allows attackers to execute code when a crafted PDF is opened. The public record identifies insecure PDF handling but does not disclose the parser routine or precise operation that overflows the stack. A victim must open the file; successful exploitation runs code in the current user's context and can crash the reader.

CVSS severity6.1
Medium
EPSS probability2.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in affected Adobe Acrobat Reader versions allows attackers to execute code when a crafted PDF is opened. The public record identifies insecure PDF handling but does not disclose the parser routine or precise operation that overflows the stack. A victim must open the file; successful exploitation runs code in the current user's context and can crash the reader.

The record

CVE
CVE-2021-39846
Published
Sep 29, 2021
Updated
Sep 16, 2024
Vendor
Adobe
Product
Adobe Acrobat Reader
Classifications
CWE-121, CWE-787, T1204.002, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=unspecified <=2017.011.30199
  2. Affected versionversion=unspecified <=2020.004.30006
  3. Affected versionversion=unspecified <=2021.005.20060
  4. Affected versionversion=unspecified <=None

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Adobe · Adobe Acrobat Readerversion=unspecified <=2017.011.30199; version=unspecified <=2020.004.30006; version=unspecified <=2021.005.20060; version=unspecified <=None

Published CVSS scores

6.1Adobe Systems IncorporatedCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
5.8NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
CWE-787Out-of-bounds Write
T1204.002User Execution: Malicious File
T1203Exploitation for Client Execution

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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