Botan EUVD-2026-113276

Requires an application that (1) uses Botan's Python binding (botan3.py) at a version >= 1.11.22 and < 3.13.0, (2) calls bcrypt() or check_bcrypt() specifically - scrypt and argon2 are unaffected, (3) passes application-controlled password strings to that binding without itself rejecting embedded NUL (U+0000) characters, and (4) enforces a password policy that validates the full string before hashing. The flaw is the Python binding's inconsistent conversion of a Python str to const char*, truncating at the embedded NUL. Limiting factors: it is confined to the Python binding (not the direct C++ API path), only bcrypt/check_bcrypt are affected, and it is inert in any application that already rejects NUL bytes in user input; no authentication is needed to supply such input (PR:N) but realistic impact depends on the calling application's policy design.

This is a low-to-moderate severity, specialized correctness flaw rather than a broad security emergency. The input CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N, base 4.8) reflects high attack complexity and limited impact, consistent with the Decision label of 'this_month' (not act_now or emergency). No EPSS score is provided and the CVE is not in CISA KEV, so there is no evidence of active or widespread exploitation; status is 'no public exploit identified at time of analysis' (the only public references are the vendor advisory, fix PR, and commit, i.e. remediation artifacts, not exploit code). The signals are internally consistent: a non-KEV, this_month library binding bug with narrow preconditions. The C:L in the supplied vector is debatable - the described impact is a password-policy bypass (weakened/effective-shorter password), which is better characterized as an integrity concern than confidentiality; this is noted rather than treated as confirmed. Real-world priority is low unless an organization specifically runs an application that uses Botan's Python binding for bcrypt-based password handling.

An application uses Botan's Python binding and enforces a password-complexity policy, calling bcrypt() to hash user-chosen passwords. A user submits a value containing an embedded NUL such as "x\0-Acceptable-Password-42!": the application's policy check sees a long, complex string and accepts it, but Botan hashes only the prefix "x", storing a trivially weak credential that defeats the policy. No public exploit code exists; the advisory supplies only an illustrative example string.