If the caller also frees this buffer then a double free will occur. In this case PEM_read_bio_ex() will return a failure code but will populate the header argument with a pointer to a buffer that has already been freed. It is possible to construct a PEM file that results in 0 bytes of payload data. The caller is responsible for freeing those buffers. If the function succeeds then the "name_out", "header" and "data" arguments are populated with pointers to buffers containing the relevant decoded data. "CERTIFICATE"), any header data and the payload data. The function PEM_read_bio_ex() reads a PEM file from a BIO and parses and decodes the "name" (e.g. See How to fix? for Alpine:3.14 relevant fixed versions and status. Note: Versions mentioned in the description apply only to the upstream openssl package and not the openssl package as distributed by Alpine:3.14. Upgrade Alpine:3.14 libretls to version 3.3.3p1-r3 or higher. ![]() ![]() It was addressed in the releases of 1.1.1n and 3.0.2 on the 15th March 2022. This issue affects OpenSSL versions 1.0.2, 1.1.1 and 3.0. In particular the attacker can use a self-signed certificate to trigger the loop during verification of the certificate signature. ![]() However any operation which requires the public key from the certificate will trigger the infinite loop. In the OpenSSL 1.0.2 version the public key is not parsed during initial parsing of the certificate which makes it slightly harder to trigger the infinite loop. Thus vulnerable situations include: - TLS clients consuming server certificates - TLS servers consuming client certificates - Hosting providers taking certificates or private keys from customers - Certificate authorities parsing certification requests from subscribers - Anything else which parses ASN.1 elliptic curve parameters Also any other applications that use the BN_mod_sqrt() where the attacker can control the parameter values are vulnerable to this DoS issue. The infinite loop can also be reached when parsing crafted private keys as they can contain explicit elliptic curve parameters. Since certificate parsing happens prior to verification of the certificate signature, any process that parses an externally supplied certificate may thus be subject to a denial of service attack. It is possible to trigger the infinite loop by crafting a certificate that has invalid explicit curve parameters. ![]() Internally this function is used when parsing certificates that contain elliptic curve public keys in compressed form or explicit elliptic curve parameters with a base point encoded in compressed form. The BN_mod_sqrt() function, which computes a modular square root, contains a bug that can cause it to loop forever for non-prime moduli. Note: Versions mentioned in the description apply only to the upstream libretls package and not the libretls package as distributed by Alpine:3.14. Upgrade Alpine:3.14 zlib to version 1.2.12-r2 or higher. Some common applications bundle the affected zlib source code but may be unable to call inflateGetHeader (e.g., see the nodejs/node reference). NOTE: only applications that call inflateGetHeader are affected. Zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in inflate.c via a large gzip header extra field. Note: Versions mentioned in the description apply only to the upstream zlib package and not the zlib package as distributed by Alpine:3.14.
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