CVE-2026-33666: Zserio is a framework for serializing structured data with a compact and efficient way with low overhead

Q: How do I fix CVE-2026-33666?

zserio: upgrade to 2.18.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-33666 being exploited?

CVE-2026-33666 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-2026-33666 affect?

CVE-2026-33666 affects zserio. Severity is high (CVSS 7.5). Zserio is a framework for serializing structured data with a compact and efficient way with low overhead. Prior to 2.18.1, in BitStreamReader.h readBytes() / readString(), the setBitPosition() bounds check receives the overflowed value and

Q: How urgent is CVE-2026-33666?

Priority 43/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-33666 is a high-severity flaw (CVSS 7.5) affecting zserio. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Zserio is a framework for serializing structured data with a compact and efficient way with low overhead. Prior to 2.18.1, in BitStreamReader.h readBytes() / readString(), the setBitPosition() bounds check receives the overflowed value and is completely bypassed. The code then reads len bytes (512 MB) from a buffer that is only a few bytes long, causing a segmentation fault. This vulnerability is fixed in 2.18.1.

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	0.3% (top 74%)
CISA exploited list	No
Weakness	CWE-190
Published	2026-04-24
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: nds-association

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-24 19:17 UTCPublished CVE record published
2026-10-26 00:10 UTCUpdated Record last modified

nds-association zserio UPGRADE

Affected: < 2.18.1

Fixed in: 2.18.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2.18.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade zserio

Note

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

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-2026-33666?

zserio: upgrade to 2.18.1. Exact commands for each OS are on this page.

Is CVE-2026-33666 being exploited?

CVE-2026-33666 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-2026-33666 affect?

CVE-2026-33666 affects zserio. Severity is high (CVSS 7.5). Zserio is a framework for serializing structured data with a compact and efficient way with low overhead. Prior to 2.18.1, in BitStreamReader.h readBytes() / readString(), the setBitPosition() bounds check receives the overflowed value and

How urgent is CVE-2026-33666?

Priority 43/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-33524 HIGH 7.5 UPGRADE Zserio is a framework for serializing structured data with a compact and efficient way with low overhead

References

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