Silent Drop of TLS 1.3 Encrypted Records in s2n-tls
Summary
| CVE | CVE-2026-16317 |
|---|---|
| State | PUBLISHED |
| Assigner | AMZN |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-21 21:16:49 UTC |
| Updated | 2026-07-22 20:37:38 UTC |
| Description | Missing validation of the outer content_type byte on TLS 1.3 encrypted records in s2n-tls allows an active man-in-the-middle to silently discard individual application data records without either endpoint detecting the modification. RFC 8446 Section 5.2 requires that the outer content_type of all encrypted TLS 1.3 records must be application_data (0x17). The s2n-tls AEAD implementation hardcodes this value in the additional authenticated data rather than using the actual wire byte, so the outer content_type is not covered by the authentication tag. This enables selective suppression of application data. In HTTP pipelining scenarios, dropping a TLS record containing an HTTP request can cause request/response desynchronization, where subsequent responses are delivered to the wrong requests. In write-heavy workloads, a dropped record containing a write request can result in undetectable data loss when the client interprets a subsequent success response as confirmation of the dropped write. All TLS 1.3 connections are affected. Both TLS clients and servers are affected. TLS 1.2 and QUIC connections are not affected. We recommend you upgrade s2n-tls to version v1.7.6 |
Risk And Classification
Primary CVSS: v4.0 8.3 HIGH from ff89ba41-3aa1-4d27-914a-91399e9639e5
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.001860000 probability, percentile 0.084470000 (date 2026-07-22)
Problem Types: CWE-354 | CWE-354 CWE-354 Improper validation of integrity check value
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | ff89ba41-3aa1-4d27-914a-91399e9639e5 | Secondary | 8.3 | HIGH | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:L/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 8.3 | HIGH | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:L/SA:N |
| 3.1 | ff89ba41-3aa1-4d27-914a-91399e9639e5 | Secondary | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L |
| 3.1 | CNA | CVSS | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
LowAttack Requirements
PresentPrivileges Required
NoneUser Interaction
NoneConfidentiality
NoneIntegrity
HighAvailability
LowSub Conf.
NoneSub Integrity
LowSub Availability
NoneCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
HighPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
HighAvailability
LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/aws/s2n-tls/security/advisories/GHSA-684c-v35q-fvx7 | ff89ba41-3aa1-4d27-914a-91399e9639e5 | github.com | |
| aws.amazon.com/security/security-bulletins/2026-062-aws | ff89ba41-3aa1-4d27-914a-91399e9639e5 | aws.amazon.com | |
| github.com/aws/s2n-tls/releases/tag/v1.7.6 | ff89ba41-3aa1-4d27-914a-91399e9639e5 | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.