Zserio Runtime: Integer Overflow in BitStreamReader and Unbounded Memory Allocation in Deserialization

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-33524: 0.32% estimated exploitation activity in the next 30 days; percentile 25.10 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Unbounded Memory Allocation (all platforms) A crafted payload as small as 4-5 bytes can force memory allocations of up to 16 GB, crashing any process with an OOM error (Denial of Service). Affected code (C++): - cpp/runtime/src/zserio/Array.h (line 1029) — mrawArray.reserve(readLength) with unchecked readLength - cpp/runtime/src/zserio/BitStreamReader.h (lines 249, 281) — value.reserve(len) with unchecked len Affected code (Java): - java/runtime/src/zserio/runtime/array/Array.java (line 271) — rawArray.reset(readSize) → new int[readSize] - java/runtime/src/zserio/runtime/io/ByteArrayBitStreamReader.java (line 245) — new byte[length] Proof of Concept Memory Allocation DoS (verified on 64-bit) | Payload | Claimed Size | Allocated | Amplification | |---------|-------------|-----------|---------------| | 4 bytes | 100,000,000 | 762 MB | ~200 million x | | 5 bytes | 2,147,483,647 | ~16 GB | system crash | The full PoC source code and Docker build files are available upon request.…

Published by the source

24 Apr 2026, 16:25 UTC

Last modified by the source

4 May 2026, 20:08 UTC

Source last checked

26 Oct 2026, 16:45 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cwq5-8pvq-j65j

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# Patch Next advisory brief: CVE-2026-33524

Advisory: Zserio Runtime: Integer Overflow in BitStreamReader and Unbounded Memory Allocation in Deserialization
IDs: CVE-2026-33524, GHSA-cwq5-8pvq-j65j
Record: https://patchnext.com/advisories/cve-2026-33524 (revision 1, source checked 26 Oct 2026, 16:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: io.github.ndsev:zserio-runtime 2.18.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.github.ndsev:zserio-runtime: affected <= 2.18.0; fixed in 2.18.1

## Suggested inspection (read-only)
- Maven io.github.ndsev:zserio-runtime: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on io.github.ndsev:zserio-runtime.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cwq5-8pvq-j65j (GitHub-reviewed advisory GHSA-cwq5-8pvq-j65j lists affected ranges: Maven io.github.ndsev:zserio-runtime >=0 <=2.18.0)

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