RewindexCVEsAmazon Web Services
CVE-2026-110310: RSA PKCS#1 v1.5 padding oracle via legacy envelope key format downgrade in Amazon S3 Encryption Client for .NET
Description
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.
Vector CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N · CWE-204, CWE-757
Tracked companies
Mapped from the CVE’s affected-product data, NVD CPE matches, vendor advisories or package feeds. A mapping means the vendor’s software is named, not that its hosted service was exposed.
Status incidents that name it
No tracked status incident names this CVE.
Affected vendors and products
Amazon: Amazon.Extensions.S3.Encryption
References
- CVE record on cve.org (opens in new tab)
- NVD entry (opens in new tab)
- aws.amazon.com/security/security-bulletins/2026-135-aws/ (opens in new tab)
- github.com/aws/amazon-s3-encryption-client-dotnet/security/advisories/GHSA-322w-… (opens in new tab)
- www.nuget.org/packages/Amazon.Extensions.S3.Encryption/3.2.2 (opens in new tab)
- www.nuget.org/packages/Amazon.Extensions.S3.Encryption/4.0.3 (opens in new tab)
- CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (opens in new tab)
- This product uses data from the NVD API but is not endorsed or certified by the NVD. (opens in new tab)
- Known Exploited Vulnerabilities catalog from CISA. (opens in new tab)
- EPSS scores from FIRST (Exploit Prediction Scoring System). (opens in new tab)