CVE-2026-88007
Description
A flaw in Traefik's HTTP/3 ConnContext allows unauthenticated remote attackers to bypass authentication on backends using connection-bound NTLM or Negotiate protocols. Missing service.AddTransportOnContext calls lead to shared kerberosRoundTripper transports, enabling attackers to hijack persistent victim backend connections, read victim-only data, and impersonate victims without credentials.
Statement
A flaw in Traefik's HTTP/3 ConnContext allows unauthenticated remote attackers to bypass authentication on backends using connection-bound NTLM or Negotiate protocols. Traefik fails to invoke service.AddTransportOnContext for HTTP/3 entrypoints, causing kerberosRoundTripper to share a single backend transport across distinct frontend connections. Under default security controls, an attacker sending requests over an existing HTTP/3 connection with backend keep-alive enabled can hijack an authenticated victim's persistent backend connection, leading to unauthorized access to sensitive victim data and impersonation without possessing victim credentials.
Mitigation
Disable HTTP/3 on Traefik entrypoints handling traffic for backends utilizing NTLM or Negotiate authentication, or disable HTTP/3 globally in the static configuration by removing or setting 'experimental.http3' / entrypoint HTTP/3 settings to false until updated packages are deployed.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 9.1 | 9.1 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data; Read Files or Directories
An attacker could bypass intended access restrictions to read sensitive data, either by reading the data directly from a data store that is not correctly restricted, or by accessing insufficiently-protected, privileged functionality to read the data.
Integrity
Technical Impact: Modify Application Data; Modify Files or Directories
An attacker could bypass intended access restrictions to modify sensitive data, either by writing the data directly to a data store that is not correctly restricted, or by accessing insufficiently-protected, privileged functionality to write the data.
Access Control
Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism
An attacker could bypass intended access restrictions to gain privileges by modifying or reading critical data directly, or by accessing privileged functionality.
Confidentiality,Integrity,Availability
Technical Impact: Execute Unauthorized Code or Commands
An attacker could use elevated privileges to execute unauthorized commands or code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
An attacker could gain unauthorized access to resources on the system and excessively consume those resources, leading to a denial of service.
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