CVE-2021-21797Public exploitNetwork attack vector

Code execution via timeout-object double free

Published Oct 18, 2021 · Updated Aug 3, 2024

Double-free in Nitro Software, Inc. Nitro Pro 13.49 and earlier allows attackers to execute code through a crafted PDF document. Its JavaScript TimeOutObject handling stores one timeout reference in two locations, then releases that reference twice when the document closes. Execution requires JavaScript to be enabled and the user to open and close the malicious document; successful exploitation runs code in the application's context.

CVSS severity8.8
High
EPSS probability15.05%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double-free in Nitro Software, Inc. Nitro Pro 13.49 and earlier allows attackers to execute code through a crafted PDF document. Its JavaScript TimeOutObject handling stores one timeout reference in two locations, then releases that reference twice when the document closes. Execution requires JavaScript to be enabled and the user to open and close the malicious document; successful exploitation runs code in the application's context.

The record

CVE
CVE-2021-21797
Published
Oct 18, 2021
Updated
Aug 3, 2024
Vendor
Nitro Software, Inc.
Product
Nitro Pro
Classifications
CWE-415, T1203, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=Nitro Pro 13.31.0.605 ,Nitro Pro 13.33.2.645

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Nitro Software, Inc. · Nitro Proversion=Nitro Pro 13.31.0.605 ,Nitro Pro 13.33.2.645

Published CVSS scores

8.8TalosCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8NIST NVDCVSS: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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-415Double Free
T1203Exploitation for Client Execution
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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