CVE-2021-28545Public exploitNetwork attack vector

Certified PDF spoofing via unchecked annotation overlays

Published Apr 1, 2021 · Updated Sep 17, 2024

Missing integrity checks in Adobe Acrobat Reader DC 2020.013.20074 and earlier allow remote attackers to alter certified PDF content. The certified-PDF validator accepts incremental updates with FreeText, Redact, or Stamp overlays; Classic 2020 2020.001.30018 and earlier and Classic 2017 2017.011.30188 and earlier are also affected. Exploitation requires a victim to open the tampered file; displayed text or images can be spoofed while the original certification remains valid.

CVSS severity8.1
High
EPSS probability2.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing integrity checks in Adobe Acrobat Reader DC 2020.013.20074 and earlier allow remote attackers to alter certified PDF content. The certified-PDF validator accepts incremental updates with FreeText, Redact, or Stamp overlays; Classic 2020 2020.001.30018 and earlier and Classic 2017 2017.011.30188 and earlier are also affected. Exploitation requires a victim to open the tampered file; displayed text or images can be spoofed while the original certification remains valid.

The record

CVE
CVE-2021-28545
Published
Apr 1, 2021
Updated
Sep 17, 2024
Vendor
Adobe
Product
Adobe Acrobat Reader
Classifications
CWE-353, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 1, 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 <=2017.011.30188
  2. Affected versionversion=unspecified <=2020.001.30018
  3. Affected versionversion=unspecified <=2020.013.20074
  4. Affected versionversion=unspecified <=None

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Adobe · Adobe Acrobat Readerversion=unspecified <=2017.011.30188; version=unspecified <=2020.001.30018; version=unspecified <=2020.013.20074; version=unspecified <=None

Published CVSS scores

8.1AdobeCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-353Missing Support for Integrity Check
T1204.002Malicious File

Public exploit references

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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