aws-kms-tls-auth vulnerable to memory overallocation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary aws-kms-tls-auth is an optional utility for s2n-tls that enables customers to use AWS KMS keys as part of the PSK extension field in a TLS 1.3 handshake. An issue exists in this library that can lead to overallocation of memory potentially resulting in a denial of service. Impact The PSK extension field in TLS 1.3 uses length-prefixed lists to encode variable-length data. aws-kms-tls-auth interprets the length prefix incorrectly resulting in additional memory allocation. s2n-tls limits ClientHello messages to 64 KB. Due to this issue, the server may allocate up to 10× the received size, meaning a single message could trigger an allocation of up to 640 KB. Repeated allocations of this size could exhaust server resources and lead to a denial-of-service. No AWS services are affected. Applications should continue to follow best practices by limiting the number of in-flight handshakes and concurrent connections. Applications using the aws-kms-tls-auth crate should upgrade to…

Published by the source

3 Mar 2026, 20:07 UTC

Last modified by the source

3 Mar 2026, 20:07 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5whh-4q9j-7v28

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# Patch Next advisory brief: GHSA-5whh-4q9j-7v28

Advisory: aws-kms-tls-auth vulnerable to memory overallocation
IDs: GHSA-5whh-4q9j-7v28
Record: https://patchnext.com/advisories/ghsa-5whh-4q9j-7v28 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: aws-kms-tls-auth 0.0.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io aws-kms-tls-auth: affected < 0.0.3; fixed in 0.0.3

## Suggested inspection (read-only)
- crates.io aws-kms-tls-auth: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on aws-kms-tls-auth.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5whh-4q9j-7v28 (GitHub-reviewed advisory GHSA-5whh-4q9j-7v28 lists affected ranges: crates.io aws-kms-tls-auth >=0 <0.0.3)

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