How severe is GHSA-cwq5-8pvq-j65j?

GHSA-cwq5-8pvq-j65j has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-cwq5-8pvq-j65j?

GHSA-cwq5-8pvq-j65j affects the following packages: io.github.ndsev:zserio-runtime (Maven). Ecosystems affected: Maven.

How do I fix GHSA-cwq5-8pvq-j65j?

Update io.github.ndsev:zserio-runtime to 2.18.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cwq5-8pvq-j65j is resolved across your whole dependency graph.

How do I detect GHSA-cwq5-8pvq-j65j in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.github.ndsev:zserio-runtime. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-cwq5-8pvq-j65j if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-cwq5-8pvq-j65j?

O3 pinpoints whether GHSA-cwq5-8pvq-j65j is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-cwq5-8pvq-j65j actively exploited in the wild?

No public exploit code has been indexed for GHSA-cwq5-8pvq-j65j yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What type of vulnerability is GHSA-cwq5-8pvq-j65j?

GHSA-cwq5-8pvq-j65j is classified as CWE-789 (CWE-789). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-cwq5-8pvq-j65j published, and has it been updated?

GHSA-cwq5-8pvq-j65j was published on April 24, 2026 and was last updated on May 5, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

GHSA-cwq5-8pvq-j65j

HIGH

GHSA-cwq5-8pvq-j65j is a high-severity (CVSS 7.5) CWE-789 vulnerability in io.github.ndsev:zserio-runtime. O3 Security confirms whether GHSA-cwq5-8pvq-j65j is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

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

Also known asCVE-2026-33524

Published

Apr 24, 2026

Updated

May 5, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Blast Radius

1 pkg affected

☕io.github.ndsev:zserio-runtime

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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) — m_rawArray.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.

Impact

zserio is the serialization framework underlying the NDS (Navigation Data Standard), used by 43 member companies including Toyota, BMW, Volkswagen, Mercedes-Benz, and others. According to the Eclipse zserio project:

"Zserio serialized data is used in millions of deployments in cars on the road"

Attack vectors include NDS.Live cloud map updates, map data supply chain compromise, and backend data processing pipelines. On 32-bit automotive ECUs, this could affect ADAS functionality.

Suggested Fix

For all runtimes: Validate varsize against stream size

if (claimedSize > remainingBytesInStream) {
    throw error("varsize claims more data than available in stream");
}

Disclosure Timeline

2026-03-08: Reported to Woven by Toyota PSIRT (go-zserio)
2026-03-10: Reported to ndsev/zserio maintainers via GitHub Security Advisory
2026-03-23: Split off overflow vulnerability to own report
90-day coordinated disclosure timeline

A patch for this issue is available at https://github.com/ndsev/zserio/releases/tag/v2.18.1.

Reporter

Ryuji Yasukochi ([email protected])

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.github.ndsev:zserio-runtime`	all versions	2.18.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.github.ndsev:zserio-runtime. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update io.github.ndsev:zserio-runtime to 2.18.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cwq5-8pvq-j65j is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-cwq5-8pvq-j65j is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-cwq5-8pvq-j65j. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## 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) — `m_rawArray.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/ru

O3 Security · Impact-Aware SCA

Is GHSA-cwq5-8pvq-j65j in your dependencies?

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