CVE-2021-25927: Prototype pollution vulnerability in 'safe-flat' versions 2.0.0 through 2.0.1 allows an attacker to cause a de

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CRITICAL 9.8REMOTEUPGRADE

CVE-2021-25927 is a critical-severity flaw (CVSS 9.8) affecting safe-flat. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Prototype pollution vulnerability in 'safe-flat' versions 2.0.0 through 2.0.1 allows an attacker to cause a denial of service and may lead to remote code execution.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.3% (top 11%)
CISA exploited list	No
Weakness	CWE-1321
Published	2021-04-26
Last modified	2026-06-17

Publisher (CNA): Mend · Vendor: safe-flat project

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

Am I affected?

Timeline

2021-04-26 11:15 UTCPublished CVE record published
2026-06-17 03:42 UTCUpdated Record last modified

safe-flat project safe-flat UPGRADE

Affected: >= 2.0.0 and < 2.0.2

Fixed in: 2.0.2

Safe to downgrade to: a release before 2.0.0

1. Check installed version

apt-cache policy safe-flat || rpm -q safe-flat || safe-flat --version

2. UPGRADE to 2.0.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade safe-flat

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade safe-flat

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.0.0 (Debian / Ubuntu)

apt-cache madison safe-flat sudo apt install safe-flat=<VERSION_BEFORE_2.0.0> sudo apt-mark hold safe-flat

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list safe-flat sudo dnf downgrade safe-flat-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add safe-flat

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-2021-25927?

safe-flat: upgrade to 2.0.2. Exact commands for each OS are on this page.

Is CVE-2021-25927 being exploited?

CVE-2021-25927 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-2021-25927 affect?

CVE-2021-25927 affects safe-flat. Severity is critical (CVSS 9.8). Prototype pollution vulnerability in 'safe-flat' versions 2.0.0 through 2.0.1 allows an attacker to cause a denial of service and may lead to remote code execution.

How urgent is CVE-2021-25927?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

References

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