CVE-2026-110310

medium

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.

References

https://www.nuget.org/packages/Amazon.Extensions.S3.Encryption/4.0.3

https://www.nuget.org/packages/Amazon.Extensions.S3.Encryption/3.2.2

https://github.com/aws/amazon-s3-encryption-client-dotnet/security/advisories/GHSA-322w-f6rw-r4fj

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-101618

https://aws.amazon.com/security/security-bulletins/2026-135-aws/

Details

Source: Mitre, NVD

Published: 2026-10-14

Updated: 2026-10-16

Risk Information

CVSS v2

Base Score: 4.9

Vector: CVSS2#AV:N/AC:H/Au:S/C:C/I:N/A:N

Severity: Medium

CVSS v3

Base Score: 5.3

Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

Severity: Medium

CVSS v4

Base Score: 6

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Severity: Medium

EPSS

EPSS: 0.00508