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No exploitation reportedFix availableAwaiting NVD analysis

CVE-2026-16317

No exploitation reported by the sources we read.

  • Published2026-07-21
  • WeaknessCWE-354

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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

Timeline

dates in UTC
  1. 2026-07-2121:16CVE publishedNVD

Versions per branch

Products declared by the CNA1 product

As AMZN, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • AWS s2n-tlsother versions: not affected
    Affected
    • ≤ 1.7.5no fix statedcustom

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-07-21

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • aws-efs-utilsSUSE:Linux Enterprise Module for Public Cloud 15 SP7all versions · fixed in 3.3.4-150600.17.12.1
  • aws-efs-utilsSUSE:Linux Enterprise Module for Public Cloud 15 SP6all versions · fixed in 3.3.4-150600.17.12.1
  • aws-efs-utilsopenSUSE:Tumbleweedall versions · fixed in 3.2.0-1.1
  • s2nopenSUSE:Tumbleweedall versions · fixed in 1.7.7-1.1
  • s2nopenSUSE:Leap 16.0all versions · fixed in 1.5.1-bp160.2.1

Vendor advisories

  • CVE-2026-16317 Red Hat Product Security

    s2n-tls: s2n-tls: Undetectable data loss via man-in-the-middle attack on TLS 1.3 records

Full record on NVD

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVE recordread 2026-10-25
  • CISA-ADPSSVC decisionnone2026-07-22
  • CNACVSS 4.08.3known since 2026-10-25
  • CNACVSS 3.16.5known since 2026-10-25
  • CNAweakness (CWE)CWE-354known since 2026-10-25
  • FIRST EPSSEPSS score0.2 %2026-11-08
  • OSVaffected packages—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
CVSS 4.0 vector
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
Published
2026-07-21
Last Modified
2026-10-24
NVD status
Awaiting Analysis

Frequently asked questions

What is CVE-2026-16317?

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

Is CVE-2026-16317 actively exploited?

Active exploitation of CVE-2026-16317 has not been confirmed. Its EPSS score was 0.2% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-16317?

CVE-2026-16317 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L.

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