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Bleichenbacher Padding Oracle in OpenSSL CMS/PKCS#7 Decryption
CVE-2019-1563 is a padding-oracle vulnerability in OpenSSL CMS/PKCS#7 RSA decryption processing, involving PKCS7_dataDecode and CMS_decrypt_set1_pkey. Applications that expose automated decryption success-or-failure notifications can enable a Bleichenbacher attack after a very large number of attacker-submitted decryption attempts. Successful exploitation can recover a CMS/PKCS#7-transported encryption key or decrypt RSA ciphertext encrypted with the corresponding public key. Affected versions are OpenSSL 1.1.1 through 1.1.1c, 1.1.0 through 1.1.0k, and 1.0.2 through 1.0.2s. Applications that supply a certificate together with the private RSA key to CMS_decrypt or PKCS7_decrypt to select the correct recipient information are not affected.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation compromises confidentiality by exposing transported CMS/PKCS#7 encryption keys or plaintext from RSA-encrypted messages associated with the affected RSA key. Recovery of a transported encryption key can also expose the message data protected by that key. The vulnerability is rated Low, with CVSS v3.0 score 3.7 and no assessed integrity or availability impact. Recovery of the RSA private key itself is not established.
If you can’t patch tonight, do this now.
Supply the appropriate recipient certificate together with the private RSA key to CMS_decrypt or PKCS7_decrypt so that the correct recipient information is selected; applications using this configuration are not affected. Avoid exposing distinguishable automated decryption success-or-failure responses to untrusted callers, since those responses provide the oracle required for exploitation. HCL BigFix lists no product-specific workaround.
Patch, then assume compromise.
Install an OpenSSL release containing the fix: 1.1.1d, 1.1.0l, or 1.0.2t for the respective affected branches, or an applicable vendor-maintained package containing a backported fix. Update affected bundled libraries and dependent products as well as system OpenSSL packages. Restart applications and services linked to the updated library, or reboot, so the corrected library is loaded. For HCL BigFix Platform, upgrade all components to version 9.2.19 using the corresponding upgrade-patch Fixlets.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
18 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.