CVE-2024-2236

What it actually does

A timing side-channel in libgcrypt's RSA decryption allows an attacker to recover plaintext from RSA ciphertexts via a Bleichenbacher-style adaptive chosen-ciphertext attack by measuring response-time differences across many decryption attempts.

Why it matters to the business

Organizations relying on libgcrypt for RSA operations face potential exposure of encrypted data such as TLS session keys, VPN credentials, or signed messages, which could lead to confidentiality breaches and require urgent patching of affected Linux distributions.

How an attack unfolds

An attacker with network access repeatedly sends specially crafted RSA ciphertexts to a target using the vulnerable libgcrypt implementation, measures subtle timing variations in the responses, and statistically reconstructs the plaintext over thousands of queries.

How to fix it

Upgrade libgcrypt to version 1.10.3 or later (or the Debian 12 package version 6.1.106-1) on all affected systems; rebuild and restart any applications statically or dynamically linked against the vulnerable library.

How to confirm the fix worked

Verify that the installed libgcrypt shared library reports version 1.10.3+ via ldconfig or package manager; run the libgcrypt self-test suite and confirm absence of the timing oracle in RSA decryption paths.

Typical attack path

1. Identify a service or application that uses libgcrypt for RSA decryption or key exchange
2. Establish network reachability to the target endpoint
3. Send a large number of adaptive chosen-ciphertext probes while recording high-resolution response times
4. Apply statistical analysis to the timing oracle to recover the RSA plaintext or private key material

How to detect it

Review application and system logs for unusually high volumes of RSA decryption operations from a single source; examine process execution history for repeated calls to libgcrypt RSA functions during suspected attack windows.

What your security team should do

• Immediately schedule patching of all Debian 12 systems using the fixed package 6.1.106-1
• Inventory applications that depend on libgcrypt and test them after the upgrade
• Monitor for any new EPSS rise or public exploit code that lowers the attack complexity