CVE-2021-39818

Arbitrary code execution via malicious TIFF handling

Published Sep 27, 2021 · Updated Sep 16, 2024

Memory corruption in Adobe InCopy allows attackers to execute arbitrary code when a user opens a malicious TIFF file. TIFF handling accesses memory beyond the end of a buffer while processing attacker-controlled image data; Adobe has not disclosed a more specific code locus. The code runs as the current user in InCopy 16.3 and earlier on Windows and 16.3.1 and earlier on macOS.

CVSS severity7.8
High
EPSS probability1.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Adobe InCopy allows attackers to execute arbitrary code when a user opens a malicious TIFF file. TIFF handling accesses memory beyond the end of a buffer while processing attacker-controlled image data; Adobe has not disclosed a more specific code locus. The code runs as the current user in InCopy 16.3 and earlier on Windows and 16.3.1 and earlier on macOS.

The record

CVE
CVE-2021-39818
Published
Sep 27, 2021
Updated
Sep 16, 2024
Vendor
Adobe
Product
InCopy
Classifications
CWE-788, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 27, 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

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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 <=16.3
  2. Affected versionversion=unspecified <=16.3.1
  3. Affected versionversion=unspecified <=None

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Adobe · InCopyversion=unspecified <=16.3; version=unspecified <=16.3.1; version=unspecified <=None

Published CVSS scores

7.8AdobeCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/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.

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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-788Access of Memory Location After End of Buffer
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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