High severity · published Apr 24, 2026
CVE-2026-33666
Zserio: Integer Overflow in BitStreamReader on 32-bit platforms
7.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 26% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ZS
zserio · ndsev
<= 2.15.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33666
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-33666
Exploit
https://github.com/ndsev/zserio/security/advisories/GHSA-fjwv-6wcr-vqwj
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CVE-2026-33524
Zserio: Integer Overflow in BitStreamReader and Unbounded Memory Allocation in Deserialization