CVE-2026-75935 in Amazon ion-java exposes a preallocation-based denial-of-service vulnerability in the library's cursor implementation. When parsing Ion binary documents, the cursor preallocates heap memory based on declared-length fields from the untrusted input stream before validating those lengths against reasonable bounds. This is a design choice—streaming parsers need expected document sizes to allocate efficiently—but it creates a DoS vector that application developers are unlikely to anticipate since the memory risk lives inside the library, not their code. The vulnerability is not novel; it follows a documented lineage through XML parsers, JSON parsers, Protocol Buffers, and Cap'n Proto implementations, representing a known failure mode that keeps recurring because the security community addresses individual CVEs rather than the underlying design pattern. The EPSS of 0.00441 indicates this sits below most scanning thresholds today, meaning the population of exposed systems is largely unmeasured—and likely to persist for years given the remediation cascade through transitive dependencies. Upgrade to 1.12.0, but examine what the patch actually does: if it only adds bounds checking without changing the preallocation strategy, similar cursor paths may remain exploitable through different input vectors. The more important question is whether this patch represents a genuine architectural shift toward lazy allocation or just another targeted fix that leaves the underlying assumption intact. High-throughput applications should benchmark against the new behavior, as the allocation strategy change can measurably affect latency under load. In distributed data pipelines, remember that cursor failures propagate upstream as backpressure and may leave downstream consumers with truncated or corrupted Ion documents that lack error signals to trigger retry logic.
CVE-2026-75935
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedUncontrolled memory allocation in the binary Ion stream cursor in Amazon ion-java before 1.12.0 might allow remote actors to cause a denial of service via a crafted Ion binary document containing a declared-length field that causes excessive heap preallocation. To remediate this issue, users should upgrade to version 1.12.0.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysisA detailed technical summary for this CVE is being prepared.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedion-java 1.12.0
- Upgrade Amazon ion-java library to version 1.12.0 or later
- If using Maven, update the dependency in pom.xml: change ion-java version to 1.12.0 or later (e.g., <version>1.12.0</version>)
- If using Gradle, update the dependency: implementation 'com.amazon.ion:ion-java:1.12.0' or later
- Rebuild and redeploy your application with the updated dependency
- Test that your application functions correctly with the new ion-java version
Generated from the published advisory — verify against the referenced sources before acting.
There is no version to upgrade to and no patch to apply. Every affected install stays exposed until the vendor ships a fix — or somebody else builds one.
Free. We build fixes in the order the community asks for them — and we’ll tell you the moment this one lands.
We develop and verify an original fix where the vendor hasn’t, from $4,900. Deployed to your staging first — never straight to production.
Scope it with usSee what else the community needs solved on the solutions-needed board.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-75935 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesCVE-2026-75935 in Amazon ion-java exposes a preallocation-based denial-of-service vulnerability in the library's cursor implementation. When parsing Ion binary documents, the cursor preallocates heap memory based on declared-length fields from the untrusted input stream before validating those lengths against reasonable bounds. This is a design choice—streaming parsers need expected document sizes to allocate efficiently—but it creates a DoS vector that application developers are unlikely to anticipate since the memory risk lives inside the library, not their code. The vulnerability is not novel; it follows a documented lineage through XML parsers, JSON parsers, Protocol Buffers, and Cap'n Proto implementations, representing a known failure mode that keeps recurring because the security community addresses individual CVEs rather than the underlying design pattern. The EPSS of 0.00441 indicates this sits below most scanning thresholds today, meaning the population of exposed systems is largely unmeasured—and likely to persist for years given the remediation cascade through transitive dependencies. Upgrade to 1.12.0, but examine what the patch actually does: if it only adds bounds checking without changing the preallocation strategy, similar cursor paths may remain exploitable through different input vectors. The more important question is whether this patch represents a genuine architectural shift toward lazy allocation or just another targeted fix that leaves the underlying assumption intact. High-throughput applications should benchmark against the new behavior, as the allocation strategy change can measurably affect latency under load. In distributed data pipelines, remember that cursor failures propagate upstream as backpressure and may leave downstream consumers with truncated or corrupted Ion documents that lack error signals to trigger retry logic.
Practitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-75935 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data