CVE-2026-59880: Immutable.js provides many Persistent Immutable data structures

Q: How do I fix CVE-2026-59880?

immutable: upgrade to 4.3.9, 5.1.8. Exact commands for each OS are on this page.

Q: Is CVE-2026-59880 being exploited?

CVE-2026-59880 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-59880 affect?

CVE-2026-59880 affects immutable. Severity is high (CVSS 7.5). Immutable.js provides many Persistent Immutable data structures. Prior to 4.3.9 and 5.1.8, Immutable.Map and Immutable.Set keep keys that share the same 32-bit hash in a HashCollisionNode collision bucket that is scanned linearly, allowing

Q: How urgent is CVE-2026-59880?

Priority 49/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-59880 is a high-severity flaw (CVSS 7.5) affecting immutable. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Immutable.js provides many Persistent Immutable data structures. Prior to 4.3.9 and 5.1.8, Immutable.Map and Immutable.Set keep keys that share the same 32-bit hash in a HashCollisionNode collision bucket that is scanned linearly, allowing an attacker who controls keys inserted into a Map, such as through Immutable.Map(obj), Immutable.fromJS(obj), state.merge(userObject), or mergeDeep, to craft many colliding keys and degrade insertion and lookup

Why this priority

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

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 48%)
CISA exploited list	No
Weakness	CWE-407
Published	2026-07-08
Last modified	2026-07-10

Publisher (CNA): GitHub, Inc. · Vendor: immutable-js

Last updated 2026-07-10 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-08 16:16 UTCPublished CVE record published
2026-07-10 18:49 UTCUpdated Record last modified

immutable-js immutable UPGRADE

Affected: < 4.3.9 · >= 5.0.0 and < 5.1.8

Fixed in: 4.3.9, 5.1.8

Safe to downgrade to: a release before 5.0.0

1. Check installed version

npm ls immutable

2. UPGRADE to 4.3.9

npm install immutable@">=4.3.9"

3. If no update is available yet, DOWNGRADE to a release before 5.0.0

npm view immutable versions npm install immutable@"<5.0.0"

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-2026-59880?

immutable: upgrade to 4.3.9, 5.1.8. Exact commands for each OS are on this page.

Is CVE-2026-59880 being exploited?

CVE-2026-59880 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-2026-59880 affect?

CVE-2026-59880 affects immutable. Severity is high (CVSS 7.5). Immutable.js provides many Persistent Immutable data structures. Prior to 4.3.9 and 5.1.8, Immutable.Map and Immutable.Set keep keys that share the same 32-bit hash in a HashCollisionNode collision bucket that is scanned linearly, allowing

How urgent is CVE-2026-59880?

Priority 49/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-59879 HIGH 7.5 UPGRADE Immutable.js provides many Persistent Immutable data structures

References

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