CVE-2021-21797: An exploitable double-free vulnerability exists in the JavaScript implementation of Nitro Pro PDF

This week

HIGH 7.8DOWNGRADE

CVE-2021-21797 is a high-severity flaw (CVSS 7.8) affecting nitro pro. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An exploitable double-free vulnerability exists in the JavaScript implementation of Nitro Pro PDF. A specially crafted document can cause a reference to a timeout object to be stored in two different places. When closed, the document will result in the reference being released twice. This can lead to code execution under the context of the application. An attacker can convince a user to open a document to trigger this vulnerability.

Why this priority

High severity
EPSS top 3%: very likely to be exploited
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	15.0% (top 3%)
CISA exploited list	No
Weakness	CWE-415
Published	2021-10-18
Last modified	2026-06-17

Publisher (CNA): Talos · Vendor: gonitro

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-10-18 13:15 UTCPublished CVE record published
2026-06-17 03:36 UTCUpdated Record last modified

gonitro nitro pro DOWNGRADE

Affected: 13.31.0.605 · 13.33.2.645

Fixed in: no fixed release known

Safe to downgrade to: a release before 13.31.0.605

1. Check installed version

apt-cache policy nitro-pro || rpm -q nitro-pro || nitro-pro --version

2. No fixed release: DOWNGRADE to a release before 13.31.0.605 (Debian / Ubuntu)

apt-cache madison nitro-pro sudo apt install nitro-pro=<VERSION_BEFORE_13.31.0.605> sudo apt-mark hold nitro-pro

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list nitro-pro sudo dnf downgrade nitro-pro-<VERSION_BEFORE_13.31.0.605> sudo dnf versionlock add nitro-pro

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-21797?

nitro pro: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-21797 being exploited?

CVE-2021-21797 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-21797 affect?

CVE-2021-21797 affects nitro pro. Severity is high (CVSS 7.8). An exploitable double-free vulnerability exists in the JavaScript implementation of Nitro Pro PDF. A specially crafted document can cause a reference to a timeout object to be stored in two different places. When closed, the document will r

How urgent is CVE-2021-21797?

Priority 56/100. High severity; EPSS top 3%: very likely to be exploited; Public exploit reference

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References

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