CVE-2021-39857Network attack vector

Local file existence disclosure via ActiveX LoadFile

Published Sep 29, 2021 · Updated Apr 23, 2025

File-existence disclosure in Adobe Acrobat Reader DC for Internet Explorer 2021.005.20060 and earlier allows remote attackers to query local paths. Public records identify the ActiveX LoadFile operation as the locus but do not disclose the faulty validation that permits the check. A victim must visit an attacker-controlled web page; affected Classic releases extend through 2020.004.30006 and 2017.011.30199, and the disclosed effect is file-existence discovery rather than file-content access.

CVSS severity3.8
Low
EPSS probability2.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

File-existence disclosure in Adobe Acrobat Reader DC for Internet Explorer 2021.005.20060 and earlier allows remote attackers to query local paths. Public records identify the ActiveX LoadFile operation as the locus but do not disclose the faulty validation that permits the check. A victim must visit an attacker-controlled web page; affected Classic releases extend through 2020.004.30006 and 2017.011.30199, and the disclosed effect is file-existence discovery rather than file-content access.

The record

CVE
CVE-2021-39857
Published
Sep 29, 2021
Updated
Apr 23, 2025
Vendor
Adobe
Product
Adobe Acrobat Reader
Classifications
CWE-200, T1083
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record 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 vectornetwork
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

4.3Adobe Systems IncorporatedCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
3.8AdobeCVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:N

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

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1083File and Directory Discovery

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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