# CVE-2026-118769: Botan: Integer overflow when reporting block size in FFI can cause memory corruption


- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 29 Oct 2026
- **Updated:** 29 Oct 2026
- **Also known as:** GHSA-c68p-822g-jfvr

## What is CVE-2026-118769?

CVE-2026-118769 is a critical vulnerability in randombit botan, published on 29 Oct 2026. 

### Official description

Botan is a C++ cryptography library. From 2.1.0 until 3.13.0, the Botan C API function botan_block_cipher_block_size converted a size_t block size to int without a bounds check. In an application that accepts external algorithm parameter strings and uses the FFI raw ECB mode, an attacker can select the variable-block-size Lion cipher so that the reported size is truncated, the caller allocates insufficient memory, and later block processing causes memory corruption. The C++ API and normally used C API modes such as CBC and CTR are unaffected. This issue is fixed in version 3.13.0.

Weakness: CWE-787 (Out-of-bounds Write), CWE-681 (Incorrect Conversion between Numeric Types), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-118769?


## How do I fix CVE-2026-118769?

No fix has been published for CVE-2026-118769 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-118769 being exploited?

There is no known exploitation of CVE-2026-118769 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-118769 and fix it if it is affected.

What it is: CVE-2026-118769 is a critical vulnerability in randombit botan, published on 29 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-118769 in the wild and no public exploit code.

Affected product: randombit botan. 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-2026-118769/ (Markdown: https://insights.sbomify.com/CVE-2026-118769/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-118769
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-118769
- OSV: https://osv.dev/vulnerability/CVE-2026-118769

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-118769/
Summaries are generated and may contain mistakes; the official description above is the record.