RSA PKCS#1 v1.5 padding oracle via legacy envelope key format downgrade in Amazon S3 Encryption Client for .NET
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.
CVE-2026-110310
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-110310
Amazon.Extensions.S3.Encryption
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "Amazon",
"product": "Amazon.Extensions.S3.Encryption",
"versions": [
{
"status": "affected",
"version": "2.1.0",
"versionType": "custom",
"lessThanOrEqual": "2.*"
},
{
"status": "affected",
"version": "3.0.0",
"versionType": "custom",
"lessThanOrEqual": "3.2.1"
},
{
"status": "affected",
"version": "4.0.0",
"versionType": "custom",
"lessThanOrEqual": "4.0.2"
}
],
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-110310
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #23107 · Revision 1
- Added to Heist Feed
- Publisher date