Amazon Extensions.S3.Encryption up to 2.1.0/3.2.1/4.0.2 Padding Scheme downgrade

Summaryinfo

A vulnerability classified as problematic has been found in Amazon Extensions.S3.Encryption up to 2.1.0/3.2.1/4.0.2. The affected element is an unknown function of the component Padding Scheme. This manipulation causes downgrade. The identification of this vulnerability is CVE-2026-110310. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Amazon Extensions.S3.Encryption up to 2.1.0/3.2.1/4.0.2 and classified as problematic. Affected by this vulnerability is some unknown processing of the component Padding Scheme. The manipulation with an unknown input leads to a downgrade vulnerability. The CWE definition for the vulnerability is CWE-757. A protocol or its implementation supports interaction between multiple actors and allows those actors to negotiate which algorithm should be used as a protection mechanism such as encryption or authentication, but it does not select the strongest algorithm that is available to both parties. As an impact it is known to affect confidentiality. The summary by CVE is:

A remote user who can read encrypted objects in the S3 bucket can force a padding downgrade by altering the padding scheme recorded in an object's metadata to legacy PKCS#1 v1.5. Since this padding scheme is susceptible to the well-known Bleichenbacher attack, the user can use a PKCS#1 v1.5 padding oracle to recover the RSA-wrapped envelope key and decrypt the object. To remediate this issue, we recommend that users upgrade to version 3.2.2 or 4.0.3. The 1.x and 2.x lines will not be patched, users of those lines need to migrate to 3.2.2 or 4.0.3.

The advisory is shared at nuget.org. This vulnerability is known as CVE-2026-110310 since 10/13/2026. The exploitation appears to be easy. The attack can be launched remotely. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1562.010 for this issue.

Upgrading to version 3.2.2 or 4.0.3 eliminates this vulnerability.

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Productinfo

Vendor

• Amazon

Name

• Extensions.S3.Encryption

Version

• 2.0
• 2.1.0
• 3.2.0
• 3.2.1
• 4.0.0
• 4.0.1
• 4.0.2

License

• commercial

CPE 2.3info

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CPE 2.2info

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