Medium · CVSS 6.0CVE-2026-110310

RSA PKCS#1 v1.5 padding oracle via legacy envelope key format downgrade in Amazon S3 Encryption Client for .NETCVE-2026-110310

Answer in brief

CVE-2026-110310 records a Medium severity (CVSS 6.0) vulnerability in RSA PKCS#1 v1.5 padding oracle via legacy envelope key format downgrade in Amazon S3 Encryption Client for .NET. The current sources do not mark it as known exploited. The current feed maps Amazon/Amazon.Extensions.S3.Encryption (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 14, 2026Updated Oct 14, 2026Source checked Oct 14, 2026First seen by HOL Oct 14, 2026Material review Oct 14, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.0
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

CVSS is 6.0. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Amazon/Amazon.Extensions.S3.Encryption (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Amazon/Amazon.Extensions.S3.Encryptiongeneric	>=2.1.0 <=2.* \|\| >=3.0.0 <=3.2.1 \|\| >=4.0.0 <=4.0.2	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Amazon/Amazon.Extensions.S3.Encryption.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Oct 14, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 14, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 14, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.