Zero Radar
← feed
CriticalVulnerabilityCVE-2026-118769updated 29 Oct 2026, 18:20 UTC

Botan cryptography library can corrupt memory via C API cipher block size

A flaw in the Botan encryption library can let an attacker corrupt a program's memory when the program lets outside users choose the encryption settings. Memory corruption can crash the program or, in some cases, let an attacker take contro

Fixed in Botan 3.13.0Official source
SeverityCriticalCVSS 9.2 of 10
Being exploited?UnclearNo reports either way yet
Fix available?YesBotan 3.13.0 · since 29 Oct 2026
How sure is this?Official sourceBacked by an official source

How the attack works simplified

  1. 1Attacker supplies parametersSelects Lion cipher via external input
  2. 2App passes to Botan C APIFFI raw ECB mode in use
  3. 3Block size truncatedsize_t cast to int, no bounds check
  4. 4Buffer too smallCaller allocates insufficient memory
  5. 5Memory corruptedOut-of-bounds block processing
  6. ResultMemory corruption in the application

What happened

The Botan C API function botan_block_cipher_block_size casts a size_t block size to int without a bounds check. An attacker who selects the variable-block-size Lion cipher in raw ECB mode via the FFI can truncate the reported size, causing undersized allocations and later out-of-bounds memory writes.

Why it is dangerous: Applications that pass external algorithm parameter strings to the Botan C API in FFI raw ECB mode can suffer memory corruption, with potential crashes or code execution. The C++ API and common C API modes such as CBC and CTR are not affected.

Are you affected?

You are affected if your application uses Botan versions 2.1.0 through 3.12.x, accepts external algorithm parameter strings, and uses the C API in raw ECB mode with the Lion cipher.

Botan 2.1.0 through 3.13.0 (exclusive): C API botan_block_cipher_block_size in FFI raw ECB mode with Lion

What to do

  1. Update Botan to version 3.13.0 or later
  2. If you cannot update now, stop accepting external algorithm parameter strings for the Lion cipher in raw ECB mode
  3. Check whether your application calls the Botan C API in raw ECB mode

Timeline

  1. 29 Oct 2026, 18:17 UTC
    Publicly disclosed
  2. 29 Oct 2026, 18:17 UTC
    Reported by NVD · NVD
  3. 29 Oct 2026, 18:20 UTC
    Picked up by Zero Radar

Sources 1 report, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-118769
CVSS
9.2 / 10
Disclosed
29 Oct 2026, 18:17 UTC
On Zero Radar
29 Oct 2026, 18:20 UTC (3 min after disclosure)
Last change
29 Oct 2026, 18:20 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

Botan cryptography library can corrupt memory via C API cipher block size · Zero Radar