{"id":"GHSA-5whh-4q9j-7v28","aliases":[],"status":"published","title":"aws-kms-tls-auth vulnerable to memory overallocation","description":"### 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. \n\ns2n-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.\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","severity":{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"low","from":"ghsa"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-119"],"published":"2026-03-03T20:07:00Z","modified":"2026-03-04T15:11:32Z","fixes":[{"ecosystem":"crates.io","package":"aws-kms-tls-auth","fixed_in":["0.0.3"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"crates.io","package":"aws-kms-tls-auth","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.0.3"}]}]},{"source":"osv","ecosystem":"crates.io","package":"aws-kms-tls-auth","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.0.3"}]}]}],"references":[{"url":"https://github.com/aws/s2n-tls/security/advisories/GHSA-5whh-4q9j-7v28","tags":["web"]},{"url":"https://github.com/advisories/GHSA-5whh-4q9j-7v28"},{"url":"https://github.com/aws/s2n-tls","tags":["package"]}],"sources":{"ghsa":[{"id":"GHSA-5whh-4q9j-7v28","title":"aws-kms-tls-auth vulnerable to memory overallocation","description":"### 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. \n\ns2n-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.\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","status":"published","published":"2026-03-03T20:07:00Z","modified":"2026-03-03T20:07:04Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"low"}],"cwes":["CWE-119"],"updated_at":"2026-11-02T14:39:30.031684Z"}],"osv":[{"id":"GHSA-5whh-4q9j-7v28","title":"aws-kms-tls-auth vulnerable to memory overallocation","description":"### 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. \n\ns2n-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.\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","status":"published","published":"2026-03-03T20:07:00Z","modified":"2026-03-04T15:11:32.782613Z","cvss":[{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"low"}],"cwes":["CWE-119"],"updated_at":"2026-11-02T15:46:38.911014Z"}]}}