CVE-2026-45820: fflate through 0.8.2 is vulnerable to denial of service via an infinite loop in unzipSync()

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-45820 is a high-severity flaw (CVSS 7.5) affecting fflate. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

fflate through 0.8.2 is vulnerable to denial of service via an infinite loop in unzipSync(). A crafted ZIP archive with a central directory entry declaring compressed_size=0xFFFFFFFF (ZIP64 sentinel) but missing the required ZIP64 extra field tag 0x0001 causes z64e() to loop indefinitely due to out-of-bounds reads returning undefined, which coerces to 0, keeping the loop condition permanently true.

Why this priority

High severity
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	0.3% (top 81%)
CISA exploited list	No
Weakness	CWE-400, CWE-835
Published	2026-07-22
Last modified	2026-10-24

Publisher (CNA): seal · Vendor: 101arrowz

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-22 08:16 UTCPublished CVE record published
2026-10-24 17:10 UTCUpdated Record last modified

101arrowz fflate UPGRADE

Affected: <= 0.8.2

Fixed in: newer than 0.8.2

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls fflate

2. UPGRADE to newer than 0.8.2

npm install fflate@">0.8.2"

Exact fixes by distribution

npm · fflate · FIXED · 0.4.9 · vulnerable: >= 0.4.5, < 0.4.9 · source

npm install fflate@">=0.4.9" npm ls fflate

Fedora 46 · newscache · FIXED · 1.3.22-1.fc46 · FEDORA-2026-49b088f8ca · source

sudo dnf upgrade --advisory=FEDORA-2026-49b088f8ca

Fedora ELN · selinux-policy · FIXED · 45.23-1.eln159 · FEDORA-2026-3668c969a2 · source

sudo dnf upgrade --advisory=FEDORA-2026-3668c969a2

RHEL 8 · grafana · NOT AFFECTED

RHEL 9 · grafana · NOT AFFECTED

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-2026-45820?

fflate: upgrade to newer than 0.8.2. Exact commands for each OS are on this page.

Is CVE-2026-45820 being exploited?

CVE-2026-45820 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-2026-45820 affect?

CVE-2026-45820 affects fflate. Severity is high (CVSS 7.5). fflate through 0.8.2 is vulnerable to denial of service via an infinite loop in unzipSync(). A crafted ZIP archive with a central directory entry declaring compressed_size=0xFFFFFFFF (ZIP64 sentinel) but missing the required ZIP64 extra fie

How urgent is CVE-2026-45820?

Priority 36/100. High severity; Remotely exploitable, no login, no user action

References

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