Vulnerability · Published Apr 24, 2026 · Assigned by GitHub_M

CVE-2026-33666Zserio: Integer Overflow in BitStreamReader on 32-bit platforms

High 7.5

In plain English

A high-severity integer overflow in zserio from ndsev. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 73.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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.

Affected products (as reported)

Vendor	Product	Versions
ndsev	zserio	<= 2.15.0

Weakness: CWE-190 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/ndsev/zserio/security/advisories/GHSA-fjwv-6wcr-vqwj x_refsource_CONFIRM