---
id: CVE-2026-118769
title: >-
  Botan: Integer overflow when reporting block size in FFI can cause memory
  corruption
summary: >-
  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…
severity: critical
cvss: 9.2
cvssVector: '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'
cvssSource: cna
cwe:
  - CWE-125
  - CWE-681
  - CWE-787
vendor: randombit
product: botan
affected:
  - 'botan >= 2.1.0, < 3.13.0'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-29T20:20:31.067238Z'
published: '2026-10-29'
updated: '2026-10-29'
sourceUpdated: '2026-10-29T20:21:04.235Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-118769'
references:
  - url: 'https://github.com/randombit/botan/security/advisories/GHSA-c68p-822g-jfvr'
    label: 'https://github.com/randombit/botan/security/advisories/GHSA-c68p-822g-jfvr'
  - url: 'https://github.com/randombit/botan/pull/5805'
    label: 'https://github.com/randombit/botan/pull/5805'
  - url: >-
      https://github.com/randombit/botan/commit/c6089ab7fab616517d56c447c93e13a5c57a0af3
    label: >-
      https://github.com/randombit/botan/commit/c6089ab7fab616517d56c447c93e13a5c57a0af3
tags:
  - cve.org
epss: 0.00365
epssPercentile: 0.30505
ingestedAt: '2026-11-03T00:33:31.381Z'
---

## Overview

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.

## Affected

- `botan >= 2.1.0, < 3.13.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.