CVE-2024-34703

What it actually does

An attacker-supplied X.509 certificate using explicit EC parameter encoding with an oversized prime (e.g., 16 Kbit) triggers an expensive primality test during parsing, resulting in high CPU consumption and denial of service.

Why it matters to the business

Applications and services that rely on Botan for certificate validation may experience resource exhaustion and outages when processing malicious certificates, affecting availability of cryptographic operations across dependent systems.

How an attack unfolds

An attacker crafts an ECDSA X.509 certificate that encodes elliptic-curve parameters explicitly with a very large prime, then presents the certificate to any Botan-based TLS handshake, certificate store, or validation routine; the library performs a primality check on the oversized parameter and exhausts CPU resources.

How to fix it

Upgrade randombit/botan to version 3.3.0, 2.19.4, or the commit 9074b04c1303a24e2084f8325fa570a5ad4f2478; rebuild and redeploy all dependent applications; disable support for explicit EC parameter encoding where possible.

How to confirm the fix worked

Verify the installed Botan version is at least 3.3.0 or 2.19.4; test that a certificate with an explicit 1024-bit or larger prime parameter is rejected within a short, bounded time; review build logs for the presence of the referenced commit.

Typical attack path

1. Craft a malicious X.509 certificate containing explicit EC parameters with a prime larger than 521 bits
2. Deliver the certificate to a vulnerable Botan implementation during TLS negotiation or certificate validation
3. Trigger the primality test on the oversized parameter
4. Consume excessive CPU until the process is terminated or the system becomes unresponsive

How to detect it

Monitor process CPU utilization and duration of certificate-parsing operations; inspect application logs for unusually large or malformed certificate structures; correlate spikes with incoming TLS or certificate-validation traffic.

What your security team should do

• Immediately update all instances of Botan to 3.3.0 or 2.19.4
• Inventory and rebuild software that statically or dynamically links against Botan
• Add runtime monitoring for sustained high CPU during certificate parsing
• Consider removing explicit EC parameter support from accepted certificate profiles