GHSA-w8gj-5xrm-gvrp: Botan: Python binding bcrypt APIs truncate passwords containing embedded NULs

Published Oct 29, 2026

Updated

Botan is a C++ cryptography library. From 1.11.22 until 3.13.0, Botan's Python binding converted Python strings containing U+0000 to const char values without consistently rejecting the embedded NUL, causing bcrypt and checkbcrypt to process only the prefix before the NUL. Applications could validate a longer password but hash a shorter effective value, allowing application password-policy bypass; scrypt and argon2 are unaffected. This issue is fixed in version 3.13.0.

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade Botan to a version that resolves this vulnerability.
Fixed in 3.13.0

Event History

Oct 29, 2026

CVE Published

via OSV·05:17 PM

Data Sourced

via OSV·05:17 PM

DescriptionSeverityWeakness

Frequently Asked Questions

Which deployments are affected?

Only applications using Botan's Python binding bcrypt or check_bcrypt APIs are affected, and only when passwords can contain an embedded U+0000 character. The issue affects versions from 1.11.22 up to, but not including, 3.13.0; scrypt and argon2 are unaffected.

What does an attacker need to exploit this?

An attacker needs to submit or use a password containing an embedded U+0000 character in an application that validates the full password but passes it to the affected bcrypt API. The bcrypt operation then processes only the portion before the NUL character.

What can be done if upgrading is not immediately possible?

Reject passwords containing U+0000 before calling Botan's Python bcrypt or check_bcrypt APIs. This prevents a longer input from being treated as a shorter prefix by bcrypt.

How can an application identify potentially affected password records or flows?

Review Python code that calls Botan's bcrypt or check_bcrypt functions and determine whether password input can contain U+0000. Authentication or registration flows that accept such input may have hashed or checked only the prefix preceding the NUL.

GHSA-w8gj-5xrm-gvrp: Botan: Python binding bcrypt APIs truncate passwords containing embedded NULs

Remediation

Event History

Frequently Asked Questions

Which deployments are affected?

What does an attacker need to exploit this?

What can be done if upgrading is not immediately possible?

How can an application identify potentially affected password records or flows?

Company

Resources

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Frequently Asked Questions

Which deployments are affected?

What does an attacker need to exploit this?

What can be done if upgrading is not immediately possible?

How can an application identify potentially affected password records or flows?