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CVE-2026-118769

Botan: Integer overflow when reporting block size in FFI can cause memory corruption

9.2 CriticalFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.36%Unchanged since Oct 30, 2026
90%50%10%1%

What each source reports

CVE List Score used 9.2

Botan: Integer overflow when reporting block size in FFI can cause memory corruption

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.

Record
CVE-2026-118769
CVSS 4.0
9.2 CriticalCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-125, CWE-681, CWE-787
Updated
2026-11-02
EUVDEUVD-2026-113278 9.2

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.

Record
EUVD-2026-113278
CVSS 4.0
9.2 CriticalCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
NVD 9.2

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.

Record
CVE-2026-118769
CVSS 4.0
9.2 CriticalCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness
CWE-125, CWE-681, CWE-787
Updated
2026-11-02
OSV 9.2

Botan: Integer overflow when reporting block size in FFI can cause memory corruption

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.

Record
CVE-2026-118769
CVSS 4.0
9.2 CriticalCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-125, CWE-681, CWE-787
Updated
2026-11-02
OSVDEBIAN-CVE-2026-118769 9.2

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.

Record
DEBIAN-CVE-2026-118769
CVSS 4.0
9.2 CriticalCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Updated
2026-11-02
OSVUBUNTU-CVE-2026-118769 9.2

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.

Record
UBUNTU-CVE-2026-118769
CVSS 4.0
9.2 CriticalCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-05
OSVAZL-112409 No score

CVE-2026-118769 affecting package botan2 2.14.0-2

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.

Record
AZL-112409
Updated
2026-11-05

Affected products

Affected packages

Affected packages
PackageAffectedFixed
botan2
Azure Linux:3
through 2.14.0-2 None known
botan
Debian:12
All versions, plus listed versions
2.19.3+dfsg-12.19.3+dfsg-1+deb12u12.19.4+dfsg-12.19.5+dfsg-12.19.5+dfsg-22.19.5+dfsg-32.19.5+dfsg-4
None known
botan
Debian:13
All versions, plus listed versions
2.19.5+dfsg-4
None known
botan3
Debian:13
All versions, plus listed versions
3.10.0+dfsg-13.10.0+dfsg-23.11.0+dfsg-13.11.1+dfsg-13.11.1+dfsg-2
Show 10 moreShow less
3.12.0+dfsg-13.12.0+dfsg-23.12.0+dfsg-2~deb13u13.13.0+dfsg-13.13.0+dfsg-23.7.1+dfsg-23.8.1+dfsg-13.9.0+dfsg-13.9.0+dfsg-23.9.0+dfsg-2.1
None known
botan3
Debian:14
before 3.13.0+dfsg-2, plus listed versions
3.10.0+dfsg-13.10.0+dfsg-23.11.0+dfsg-13.11.1+dfsg-13.11.1+dfsg-2
Show 9 moreShow less
3.12.0+dfsg-13.12.0+dfsg-23.12.0+dfsg-2~deb13u13.13.0+dfsg-13.7.1+dfsg-23.8.1+dfsg-13.9.0+dfsg-13.9.0+dfsg-23.9.0+dfsg-2.1
3.13.0+dfsg-2
botan
Ubuntu:18.04:LTS
All versions, plus listed versions
2.4.0-32.4.0-42.4.0-5ubuntu1
None known
botan
Ubuntu:20.04:LTS
All versions, plus listed versions
2.9.0-22.9.0-2build12.12.1-22.12.1-2build1
None known
botan
Ubuntu:Pro:22.04:LTS
All versions, plus listed versions
2.17.3+dfsg-32.19.1+dfsg-2ubuntu12.19.1+dfsg-2ubuntu1+esm1
None known
botan
Ubuntu:Pro:24.04:LTS
All versions, plus listed versions
2.19.3+dfsg-1ubuntu12.19.3+dfsg-1ubuntu22.19.3+dfsg-1ubuntu2+esm1
None known

History

History
RecordedChangedSources
factsOSV
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-118769 is a critical vulnerability (CVSS 9.2) in Randombit Botan, published October 29, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.36%, the 30th percentile. Fixed in botan3 3.13.0+dfsg-2.

References

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