Vulnerability · Published Oct 29, 2026 · Assigned by GitHub_M

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

Critical 9.2

In plain English

A critical-severity out-of-bounds read in botan from randombit. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 30% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)9.2Critical

Exploit odds (30 days)0.4%top 69.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	botan	no fix listed	DEBIAN-CVE-2026-118769
Debian:13	botan	no fix listed	DEBIAN-CVE-2026-118769
Debian:13	botan3	no fix listed	DEBIAN-CVE-2026-118769
Debian:14	botan3	3.13.0+dfsg-2	DEBIAN-CVE-2026-118769

Affected products (as reported)

Vendor	Product	Versions
randombit	botan	>= 2.1.0, < 3.13.0

Weakness: CWE-125, CWE-681, CWE-787 · Vector: 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

References

https://github.com/randombit/botan/security/advisories/GHSA-c68p-822g-jfvr x_refsource_CONFIRM
https://github.com/randombit/botan/pull/5805 x_refsource_MISC
https://github.com/randombit/botan/commit/c6089ab7fab616517d56c447c93e13a5c57a0af3 x_refsource_MISC