CVE-2026-110310
Published:October 14, 2026
Updated:October 15, 2026
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.
Affected Packages
Amazon.Extensions.S3.Encryption (DOT_NET):
Affected version(s) >=3.2.0.0 <3.2.2Fix Suggestion:
Update to version 3.2.2Amazon.Extensions.S3.Encryption (DOT_NET):
Affected version(s) >=4.0.0.0 <4.0.3Fix Suggestion:
Update to version 4.0.3amazon.extensions.s3.encryption (NUGET):
Affected version(s) >=3.2.0 <3.2.2Fix Suggestion:
Update to version 3.2.2amazon.extensions.s3.encryption (NUGET):
Affected version(s) >=4.0.0 <4.0.3Fix Suggestion:
Update to version 4.0.3Related Resources (4)
Do you need more information?
Contact UsCVSS v4
Base Score:
6
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
EPSS
Base Score:
0.51