Botan CVE-2026-44378

The vulnerability is triggered when the application passes externally-supplied BER-encoded data to Botan's parser, specifically data containing particular patterns of indefinite-length encodings. No authentication is required (CVSS PR:N confirms unauthenticated exploitation). The attack is fully remote (AV:N) with low complexity (AC:L) and no user interaction (UI:N), meaning any network-reachable Botan-based service that processes attacker-influenced ASN.1 input is exposed. Exploitation is limited to denial of service - there is no code execution, privilege escalation, or data disclosure path. The condition that limits risk: applications that only process BER/DER data generated internally or from trusted, authenticated sources are not practically exploitable. Services that enforce strict input size caps may also limit the quadratic blowup to sub-impactful levels.

The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) confirms unauthenticated remote exploitation with no prerequisites beyond network reachability and no user interaction required, making automated scanning and exploitation straightforward. However, impact is narrowly scoped to local availability (VA:L) with no confidentiality or integrity consequences, reflecting a CPU exhaustion scenario rather than data compromise or code execution. No EPSS score was provided in the input data, preventing quantitative exploitation likelihood comparison. The vulnerability is not listed in CISA KEV and no public exploit code exists at time of analysis, indicating this is not currently under active widespread attack. Real-world priority is moderate: applications that parse untrusted BER/DER input from the network (e.g., TLS certificate validation, S/MIME parsing, OCSP responses) face genuine DoS exposure, while those processing only internally-generated or trusted data face negligible risk. The low availability impact score (VA:L rather than VA:H) suggests the quadratic behavior is resource-intensive but may not instantly crash services on small inputs.

An attacker sends a crafted BER-encoded payload - such as a malformed X.509 certificate during a TLS handshake or a manipulated CMS/PKCS#7 message - to a service built on Botan for cryptographic parsing. The payload contains deliberately nested or repeated indefinite-length encoding patterns that cause the parser to perform quadratic work relative to input size. By sending multiple such payloads concurrently or in rapid succession, the attacker drives CPU utilization to capacity, degrading or denying service to legitimate users. No public proof-of-concept code has been identified at time of analysis.