php: potential exposure to Marvin attack via unsafe implementation of RSA decryption API

Publication Date2024-06-07
TypeInformation Disclosure
Affected PHP Versions
  • 5.6.0-7.1.33
  • 7.2.0-7.2.34
  • 7.3.0-7.3.33
  • 7.4.0-7.4.33
  • 8.0.0-8.0.30
  • 8.1.0-8.1.28
  • 8.2.0-8.2.19
  • 8.3.0-8.3.7
Fixed Product Versions
  • ZendPHP 7.2
  • ZendPHP 7.3
  • ZendPHP 7.4
  • ZendPHP 8.0
  • ZendPHP 8.1
  • ZendPHP 8.2
  • ZendPHP 8.3
  • ZendServer 2021.3.5

CVE Details

The openssl_private_decrypt function in PHP, when using PKCS1 padding (OPENSSL_PKCS1_PADDING, which is the default), is vulnerable to the Marvin Attack unless it is used with an OpenSSL version that includes the changes from this pull request: (rsa_pkcs1_implicit_rejection). These changes are part of OpenSSL 3.2 and have also been backported to stable versions of various Linux distributions, as well as to the PHP builds provided for Windows since the previous release. All distributors and builders should ensure that this version is used to prevent PHP from being vulnerable. PHP Windows builds for the versions 8.1.29, 8.2.20 and 8.3.8 and above include OpenSSL patches that fix the vulnerability. The RSA decryption implementation using PKCS#1 v1.5 padding in OpenSSL is vulnerable to a timing side-channel attack known as the Marvin Attack. This vulnerability arises because the execution time of the openssl_private_decrypt() function in PHP with OpenSSL varies based on whether a valid message is returned. This flaw allows an attacker to use these timing differences to decrypt captured ciphertexts or forge signatures, compromising the security of the encrypted data. The vulnerability has been demonstrated through statistical analysis of execution times, confirming the presence of a side channel that can be leveraged in a Bleichenbacher-style attack.


We recommend ensuring that your OpenSSL installation is up-to-date, and, if using Windows binaries, that they were compiled against patched OpenSSL versions.

ZendPHP is always compiled using patched OpenSSL versions.