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Prior to version 3.12.0, Botan’s ASN.1 BER decoder accepted indefinite‑length encodings even inside structures that the relevant standard (DER) requires to be encoded with definite lengths. When parsing a specially crafted BER message that nests many indefinite‑length constructs, the parser exhibited quadratic time complexity – each new nested level caused a rescan of the already‑processed data. An attacker able to feed untrusted ASN.1 data (e.g., a malicious X.509 certificate or OCSP response) into an application that uses Botan could exploit this behavior. By sending a relatively small payload that triggers the pathological parsing pattern, the attacker can force the CPU usage to grow quadratically with the input size, leading to a denial of service (DoS). The vulnerability is fixed in Botan 3.12.0, which now enforces strict DER encoding for PKIX types and introduces a `BER_Decoder::Limits` mechanism to reject indefinite length encodings where they are not allowed.
DailyCVE Form:
Platform: Botan
Version: 3.0.0‑3.11.x
Vulnerability: Inefficient algorithmic complexity
Severity: Medium
Date: 2026‑05‑06
Prediction: Upgrade to 3.12.0
What Undercode Say: Analytics
Check Botan version botan version Ubuntu 26.04 LTS (Resolute) – status: Needs evaluation apt show botan3 Fedora 44 – check for fixed package dnf update botan3
Vulnerable pattern: indefinite length encoding (0x80) Example ASN.1 fragment that triggers quadratic parsing ber_data = b'\x30\x80' + b'\x30\x80' 1000 + b'\x00\x00'
Exploit
A remote attacker can craft an ASN.1‑encoded message (e.g., an X.509 certificate with deeply nested indefinite‑length SEQUENCEs) and deliver it to any Botan‑based service that parses untrusted BER data. As the parser processes each nested indefinite length, it rescans the already‑decoded portion, leading to O(n²) CPU consumption. A relatively small message (a few kilobytes) can cause seconds or minutes of CPU spike, effectively starving the application thread.
Protection
- Upgrade to Botan 3.12.0 or later.
- If immediate upgrade is not possible, apply the backported patch that rejects indefinite length encodings in DER‑mandated structures (see vendor advisory).
- Validate that all input ASN.1 data is strict DER before passing it to the Botan BER decoder.
- Monitor CPU usage for unusual spikes when processing certificates or other ASN.1 inputs.
Impact
- Availability: High – unauthenticated remote DoS.
- Confidentiality / Integrity: None – the flaw does not leak data or allow code execution.
- Attack complexity: Low – the attacker needs only to send a single crafted BER message.
- Privileges required: None – no prior authentication needed.
- User interaction: None – the attack works without any user action.
> All information above is based on publicly available data for CVE‑2026‑44378. Always refer to the official Botan release notes and security advisories for the most accurate and up‑to‑date guidance.
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Sources:
Reported By: nvd.nist.gov
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