Medium · published September 29, 2026
Issue summary: A certificate with many nameRelativeToCRLIssuer CRL
distribution points causes disproportionate heap growth when OpenSSL caches
X.509 extensions.
Impact summary: Receiving a crafted certificate from a malicious peer can lead
to significant memory pressure and possible Denial of Service in clients or
in servers that solicit client certificates.
CWE: CWE-770: Allocation of Resources Without Limits or Throttling
Description: A certificate or a set of certificates that fits under the limit for
size of certificates accepted from the peer (~100 KiB) can result in allocation
of several hundred MiB of resident memory on the receiving side
during a normal TLS handshake. This may be enough to crash the client or
server, if multiple concurrent connections lead to similarly large memory
allocations.
The fix postpones processing of the CRL distribution points extensions in
certificates to the time when the processed value is required for CRL processing.
This avoids keeping large memory allocations for a long time when such
certificates are received.
FIPS impact: no
The affected code is outside the FIPS module boundary.
| Product | Versions | Fixed in |
|---|---|---|
| openssl/openssl | ≥ 1.0.2, < 1.0.2zs | 1.0.2zs |
| openssl/openssl | ≥ 1.1.1, < 1.1.1zj | 1.1.1zj |
| openssl/openssl | ≥ 3.0.0, < 3.0.23 | 3.0.23 |
| openssl/openssl | ≥ 3.4.0, < 3.4.8 | 3.4.8 |
| openssl/openssl | ≥ 3.5.0, < 3.5.9 | 3.5.9 |
| openssl/openssl | ≥ 3.6.0, < 3.6.5 | 3.6.5 |
| openssl/openssl | ≥ 4.0.0, < 4.0.3 | 4.0.3 |