Read the docs
TI-2026-74450 Aliases CVE-2026-110310

Padding oracle in Amazon S3 Encryption Client for .NET

Priority LOW 27CWE-204Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Attack requirements
Present
Impact type
Information disclosure
Confidentiality · integrity · availability
High · None · None
Fix status
No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-204.

Summary

Amazon.Extensions.S3.Encryption, the Amazon S3 Encryption Client for .NET, is affected in versions 2.1.0 through 2.*, 3.0.0 through 3.2.1 and 4.0.0 through 4.0.2. A remote user who can read encrypted objects can downgrade the object's padding to legacy PKCS#1 v1.5 (CWE-757). That padding is open to Bleichenbacher attacks, so the user can recover the RSA-wrapped envelope key and decrypt the object.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00508 43rd percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
AWSAmazon.Extensions.S3.Encryption2.1.0 and later; 3.0.0 – 3.2.1; 4.0.0 – 4.0.2—No fix listedCNA
  • Amazon.Extensions.S3.Encryption VendorAWS Affected 2.1.0 and later; 3.0.0 – 3.2.1; 4.0.0 – 4.0.2 Fixed in — No fix listed CNA

Remediation

Upgrade Amazon.Extensions.S3.Encryption to version 3.2.2 or 4.0.3. The 1.x and 2.x lines will not be patched, so users of those lines need to migrate to 3.2.2 or 4.0.3.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-15 Threatist record created from CVE-2026-110310
  2. 2026-11-06 Affected versions changed · Red Hat
  3. 2026-11-06 CVSS score added · Red Hat

References

Patch 2

Advisory 2

  • TI-2026-23989 crypto: algif_aead - Revert to operating out-of-place KEVCVSS 3.1HIGH 7.8
  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2024-18648 Amazon AWS Amplify CLI before 12.10.1 incorrectly configures the role trust policy of IAM… CVSS 3.1CRITICAL 9.8
  • TI-2024-05929 Openssh: regresshion - race condition in ssh allows rce/dos CVSS 3.1HIGH 8.1
  • TI-2025-03847 Input validation issue in AWS Amplify Studio UI component properties CVSS 4.0CRITICAL 9.0
  • TI-2026-11603 HTTP/2 Stream Parser Confusion Body-Inspection Bypass in Amazon CloudFront with AWS WAF CVSS 4.0HIGH 7.9
See all 383 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences