CVE-2023-45853: MiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFile

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CRITICAL 9.8REMOTEUPGRADEUPGRADE

CVE-2023-45853 is a critical-severity flaw (CVSS 9.8) affecting zlib, pyminizip. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

MiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFileInZip4_64 via a long filename, comment, or extra field. NOTE: MiniZip is not a supported part of the zlib product. NOTE: pyminizip through 0.2.6 is also vulnerable because it bundles an affected zlib version, and exposes the applicable MiniZip code through its compress API.

Why this priority

Critical severity
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	3.4% (top 11%)
CISA exploited list	No
Weakness	CWE-190
Published	2023-10-14
Last modified	2026-10-15

Publisher (CNA): MITRE · Vendor: smihica · zlib

Last updated 2026-10-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-10-14 02:15 UTCPublished CVE record published
2026-10-15 00:16 UTCUpdated Record last modified

zlib zlib UPGRADE

Affected: < 1.3.1

Fixed in: 1.3.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy zlib || rpm -q zlib || zlib --version

2. UPGRADE to 1.3.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade zlib

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade zlib

Note

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

smihica pyminizip UPGRADE

Affected: <= 0.2.6

Fixed in: newer than 0.2.6

Safe to downgrade to: no unaffected older release

1. Check installed version

pip show pyminizip

2. UPGRADE to newer than 0.2.6

pip install --upgrade "pyminizip>0.2.6"

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-2023-45853?

zlib: upgrade to 1.3.1; pyminizip: upgrade to newer than 0.2.6. Exact commands for each OS are on this page.

Is CVE-2023-45853 being exploited?

CVE-2023-45853 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-2023-45853 affect?

CVE-2023-45853 affects zlib, pyminizip. Severity is critical (CVSS 9.8). MiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFileInZip4_64 via a long filename, comment, or extra field. NOTE: MiniZip is not a supported part of the zlib product. NOTE: pyminizip

How urgent is CVE-2023-45853?

Priority 62/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

zlib vulnerabilities

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References

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