# CVE-2026-15997: Native ARM SHA3 / SHAKE `restoreFullState` fails to detect size_t underflow in a crafted encoded state

> An integer underflow in ARM SHA3/SHAKE state restoration allows out-of-bounds writes, potentially leading to code execution or denial of service.

- **Severity:** Low 1.7 (`CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/S:P/AU:N/R:A/V:D/RE:M/U:Amber`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 16 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** GHSA-hcmw-xv23-7hqq, UBUNTU-CVE-2026-15997

## What is CVE-2026-15997?

CVE-2026-15997 is a low-severity vulnerability in Legion of the Bouncy Castle Inc. BC-LTS, published on 16 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Out-of-bounds write vulnerability in Legion of the Bouncy Castle Inc. BC-LTS bcprov-lts8on on ARM allows Overflow Buffers.

 This vulnerability is associated with program files https://github.Com/bcgit/bc-lts-java/blob/main/native_c/arm/sha/shake.C, https://github.Com/bcgit/bc-lts-java/blob/main/native_c/arm/sha/sha3.C.

This issue affects BC-LTS: from 2.73.0 before 2.73.12.1.

Issue is only applicable if application involved is accepting memoable SHA3 / SHAKE states from potentially untrusted sources.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-15997?


## How do I fix CVE-2026-15997?

No fix has been published for CVE-2026-15997 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-15997 being exploited?

There is no known exploitation of CVE-2026-15997 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-15997 and fix it if it is affected.

What it is: CVE-2026-15997 is a low-severity vulnerability in Legion of the Bouncy Castle Inc. BC-LTS, published on 16 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-15997 in the wild and no public exploit code.

Affected product: Legion of the Bouncy Castle Inc. BC-LTS. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-15997/ (Markdown: https://insights.sbomify.com/CVE-2026-15997/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-15997
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15997
- OSV: https://osv.dev/vulnerability/CVE-2026-15997

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-15997/
Summaries are generated and may contain mistakes; the official description above is the record.