CVE-2026-26021: set-in provides the set value of nested associative structure given array of keys

Q: How urgent is CVE-2026-26021?

Priority 56/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-26021 is a critical-severity flaw (CVSS 9.8) affecting set-in. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

set-in provides the set value of nested associative structure given array of keys. A prototype pollution vulnerability exists in the the npm package set-in (>=2.0.1, < 2.0.5). Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using Array.prototype. This has been fixed in version 2.0.5.

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	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-1321
Published	2026-02-11
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: set-in project

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

Am I affected?

Timeline

2026-02-11 22:15 UTCPublished CVE record published
2026-06-17 10:25 UTCUpdated Record last modified

set-in project set-in UPGRADE

Affected: >= 2.0.1 and < 2.0.5

Fixed in: 2.0.5

Safe to downgrade to: a release before 2.0.1

1. Check installed version

apt-cache policy set-in || rpm -q set-in || set-in --version

2. UPGRADE to 2.0.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade set-in

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade set-in

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 2.0.1 (Debian / Ubuntu)

apt-cache madison set-in sudo apt install set-in=<VERSION_BEFORE_2.0.1> sudo apt-mark hold set-in

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

dnf --showduplicates list set-in sudo dnf downgrade set-in-<VERSION_BEFORE_2.0.1> sudo dnf versionlock add set-in

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.

Exact fixes by distribution

npm · set-in · FIXED · 2.0.5 · vulnerable: >= 2.0.1, < 2.0.5 · source

npm install set-in@">=2.0.5" npm ls set-in

Fedora ELN · fwupd-efi · FIXED · 1.9-3.eln159 · FEDORA-2026-44fd42db42 · source

sudo dnf upgrade --advisory=FEDORA-2026-44fd42db42

Fedora 46 · crest · FIXED · 3.0.2-1.fc46 · FEDORA-2026-b49adefa8f · source

sudo dnf upgrade --advisory=FEDORA-2026-b49adefa8f

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/ahdinosaur/set-in/security/advisories/GHSA-2c4m-g7rx-63q7

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-2026-26021?

set-in: upgrade to 2.0.5. Exact commands for each OS are on this page.

Is CVE-2026-26021 being exploited?

CVE-2026-26021 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-2026-26021 affect?

CVE-2026-26021 affects set-in. Severity is critical (CVSS 9.8). set-in provides the set value of nested associative structure given array of keys. A prototype pollution vulnerability exists in the the npm package set-in (>=2.0.1, < 2.0.5). Despite a previous fix that attempted to mitigate prototype poll

How urgent is CVE-2026-26021?

Priority 56/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

npm packages vulnerabilities

References

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