GHSA-5WHH-4Q9J-7V28
Vulnerability from github – Published: 2026-03-03 20:07 – Updated: 2026-03-03 20:07Summary
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. 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
{
"affected": [
{
"package": {
"ecosystem": "crates.io",
"name": "aws-kms-tls-auth"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.0.3"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-119"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-03T20:07:00Z",
"nvd_published_at": null,
"severity": "LOW"
},
"details": "### Summary\naws-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.\n\n### Impact\nThe 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.\u00a0\n\ns2n-tls limits ClientHello messages to 64 KB. Due to this issue, the server may allocate up to 10\u00d7 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.\n\nNo 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.\n\n**Impacted versions:** \u003c 0.0.3\n\n### Patches\nThis issue has been addressed in aws-kms-tls-auth v0.0.3 [1].\n\n### Workarounds\nThere is no workaround. Applications using aws-kms-tls-auth should upgrade to the most recent release.\n\n### Acknowledgement \ns2n-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.\n\nIf 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.\n\n[1] https://crates.io/crates/aws-kms-tls-auth/0.0.3\n[2] Vulnerability reporting page: https://aws.amazon.com/security/vulnerability-reporting",
"id": "GHSA-5whh-4q9j-7v28",
"modified": "2026-03-03T20:07:00Z",
"published": "2026-03-03T20:07:00Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/aws/s2n-tls/security/advisories/GHSA-5whh-4q9j-7v28"
},
{
"type": "PACKAGE",
"url": "https://github.com/aws/s2n-tls"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
"type": "CVSS_V3"
}
],
"summary": "aws-kms-tls-auth vulnerable to memory overallocation"
}
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