# GHSA-5whh-4q9j-7v28: aws-kms-tls-auth vulnerable to memory overallocation > A memory overallocation flaw in aws-kms-tls-auth allows remote attackers to cause denial of service via crafted TLS handshakes. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 3 Mar 2026 ## What is GHSA-5whh-4q9j-7v28? GHSA-5whh-4q9j-7v28 is a denial of service vulnerability in aws-kms-tls-auth, published on 3 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description ### 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 version 0.0.3. **Impacted versions:** < 0.0.3 ### Patches This issue has been addressed in aws-kms-tls-auth v0.0.3 [1]. ### Workarounds There is no workaround. Applications using aws-kms-tls-auth should upgrade to the most recent release. ### Acknowledgement s2n-tls would like to thank Joshua Rogers (https://joshua.hu/) of AISLE Research Team (https://aisle.com/) for collaborating on this issue through the coordinated disclosure process. If there are any questions or comments about this advisory, contact AWS/Amazon Security via the vulnerability reporting page [2] or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). Please do not create a public GitHub issue. [1] https://crates.io/crates/aws-kms-tls-auth/0.0.3 [2] Vulnerability reporting page: https://aws.amazon.com/security/vulnerability-reporting ## Which versions are affected by GHSA-5whh-4q9j-7v28? 2 open source packages ship an affected version, including aws-kms-tls-auth. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `aws-kms-tls-auth` | crates.io | All versions | 0.0.3 | | `aws-kms-tls-auth` | crates.io | All versions | 0.0.3 | ## How do I fix GHSA-5whh-4q9j-7v28? Upgrade aws-kms-tls-auth to 0.0.3 or later. ## Is GHSA-5whh-4q9j-7v28 being exploited? There is no known exploitation of GHSA-5whh-4q9j-7v28 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for GHSA-5whh-4q9j-7v28 and fix it if it is affected. What it is: GHSA-5whh-4q9j-7v28 is a denial of service vulnerability in aws-kms-tls-auth, published on 3 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of GHSA-5whh-4q9j-7v28 in the wild and no public exploit code. Affected packages and fixed versions: - aws-kms-tls-auth (crates.io): affected all versions; fixed in 0.0.3 - aws-kms-tls-auth (crates.io): affected all versions; fixed in 0.0.3 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/GHSA-5whh-4q9j-7v28/ (Markdown: https://insights.sbomify.com/GHSA-5whh-4q9j-7v28/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/GHSA-5whh-4q9j-7v28 --- From sbomify Insights: https://insights.sbomify.com/GHSA-5whh-4q9j-7v28/ Summaries are generated and may contain mistakes; the official description above is the record.