VulnerabilityPublished 6 Aug 2026

CVE-2026-54765: Traefik · Gateway HTTPRoute backendRef filters can leak backend context across routes sharing a Service:port

Affects github.com/traefik/traefik/v3Source GCVE Database

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Not known to be exploited · CVSS 6.3 Medium : upgrade to 3.7.6 when convenient.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 4.0 base score

6.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 28% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.7.6

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:H/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: High
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
Subsequent system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Subsequent System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 6 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade github.com/traefik/traefik/v3 to 3.7.6.

Affected software

Product	Affected	Fixed in
Gogithub.com/traefik/traefik/v3	Affected >=3.7.0 <3.7.6	Fixed in 3.7.6

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

An official patch is available in Traefik version 3.7.6. Users should upgrade to this version or later to remediate the vulnerability. No additional mitigation steps are required if the patch is applied. Patch status is confirmed by the vendor advisory.

Description

## Summary There is a medium severity vulnerability in Traefik's Kubernetes Gateway API provider. When two accepted HTTPRoutes target the same backend Service:port but configure different `backendRef` filters, Traefik may resolve both routes to the same child service and apply only one route's filter set to all requests reaching that backend. In Gateway deployments where `backendRef` filters set security-sensitive headers — such as tenant identity, authorization context, or values the backend trusts — an attacker who can create an accepted HTTPRoute sharing the same backend Service:port may cause their route's filter context to be applied to another route's requests, potentially crossing namespace boundaries when a `ReferenceGrant` permits cross-namespace targeting. ## Patches - https://github.com/traefik/traefik/releases/tag/v3.7.6 ## For more information If you have any questions or comments about this advisory, please [open an issue](https://github.com/traefik/traefik/issues). <details> <summary>Original Description</summary> # Traefik Gateway HTTPRoute backendRef filter context collision across routes sharing Service:port ## Summary Traefik's Kubernetes Gateway API provider builds the dynamic HTTP backend service key for a Gateway `HTTPRoute` backendRef from only the backend namespace, Service name, protocol, and port. It does not include the HTTPRoute, listener, rule, or backendRef filter identity in that key. When two accepted HTTPRoutes point to the same backend `Service:port` but define different backendRef filters, Traefik can make both route WRR services reference the same child service. The child service then carries only one backendRef filter set, so one route can send requests to the backend with another route's backend context. This is security-relevant when backendRef filters set, remove, or rewrite security-sensitive context, such as tenant, identity, auth, sanitization, Host, or path headers trusted by the backend. Credit: Qican Ma, Ding Luo @XiaoMi ShadowBlade Security Lab ## Suggested Severity Suggested severity: Medium/High, configuration-dependent. Suggested CVSS 3.1: ```text CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:H/A:N ``` Notes: - Requires Gateway API routes sharing the same backend Service:port with different security-sensitive backendRef filters trusted by the backend. - Cross-namespace impact is possible when route attachment and ReferenceGrant policy allow an attacker route to target the shared backend. - No RCE, memory corruption, or default-config exposure claimed. Suggested CWE: ```text CWE-863: Incorrect Authorization CWE-284: Improper Access Control ``` ## Affected Component ```text pkg/provider/kubernetes/gateway/httproute.go — loadService(), loadMiddlewares() ``` ## Tested Versions Confirmed on: ```text Traefik source snapshot: 29406d42898547f1ffabd904f66af06c212740cf on master ``` Earliest affected version not exhaustively determined. ## Root Cause `loadService` starts the dynamic service name from backend namespace and Service name only: ```go // pkg/provider/kubernetes/gateway/httproute.go:245 serviceName := provider.Normalize(namespace + "-" + string(backendRef.Name) + "-http") ``` It loads backendRef filters using that same service name before appending the backend port: ```go // pkg/provider/kubernetes/gateway/httproute.go:258 middlewares, err := p.loadMiddlewares(conf, namespace, serviceName, backendRef.Filters, pathMatch) ``` For normal Kubernetes Services, the final child service key appends only the port: ```go // pkg/provider/kubernetes/gateway/httproute.go:304-317 portStr := strconv.FormatInt(int64(port), 10) serviceName = provider.Normalize(serviceName + "-" + portStr) ... conf.HTTP.Services[serviceName] = &dynamic.Service{LoadBalancer: lb, Middlewares: middlewares} ``` Each route/rule WRR service references the child service by name. Later route configs are merged by map key (`maps.Copy`), so both route-local WRR services can point to the same child service, which retains only one of the route/backendRef filter configurations. ## Attack Scenario 1. Gateway listener with `allowedRoutes.namespaces.from: All`. 2. Victim `HTTPRoute` `route-a` in namespace `default` targets `default/whoami:80` with backendRef filter setting `X-Tenant: tenant-a`. 3. Attacker-controlled `HTTPRoute` `route-b` in namespace `attacker` targets `default/whoami:80` (via ReferenceGrant) with backendRef filter setting `X-Tenant: tenant-b`. 4. Both routes generate the same child service key: `default-whoami-http-80`. 5. The second route's filter configuration overwrites the first (or vice versa) via `maps.Copy`. 6. Backend receives both routes' requests with one tenant's header context. ## Proof of Concept A Go test harness injects provider-level and server-level tests into the Traefik checkout. The provider test confirms the generated dynamic configuration collision. The server test builds Traefik's runtime router/service/middleware pipeline and sends `h

Impact

An attacker who can create an accepted HTTPRoute sharing the same backend Service:port as a victim route may cause their backendRef filter context to be applied to the victim's requests. This can result in leakage of security-sensitive headers such as tenant identity or authorization context across routes, potentially crossing namespace boundaries if ReferenceGrant policies permit. There is no indication of remote code execution, memory corruption, or exposure of default configurations. The impact is primarily unauthorized access or incorrect authorization context being applied to backend requests.

Summary

Traefik's Kubernetes Gateway API provider constructs backend service keys using only the backend namespace, Service name, protocol, and port, omitting route-specific filter identities. When two HTTPRoutes target the same backend Service:port but specify different backendRef filters, Traefik may merge these routes to the same child service, which retains only one set of backendRef filters. This causes requests from one route to be processed with another route's backend context, including security-sensitive headers such as tenant identity or authorization context. This vulnerability is configuration-dependent and can lead to cross-namespace security context leakage when ReferenceGrant policies allow cross-namespace targeting. The vulnerability was confirmed on Traefik source snapshot 29406d42898547f1ffabd904f66af06c212740cf on master and affects versions >=3.7.0 <3.7.6. An official fix is available in version 3.7.6.

CWE-284Improper Access Control (opens in a new tab)
Pillar weaknessCWE Top 25 (2025): #19OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Operation
Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
OWASP Cheat Sheets
Docker Security (opens in a new tab)
Third Party Javascript Management (opens in a new tab)
Virtual Patching (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V1.4.4 (opens in a new tab)
V1.4.5 (opens in a new tab)
V1.10.1 (opens in a new tab)
Attack patterns
Embedding Scripts within Scripts (opens in a new tab)
Modification of Windows Service Configuration (opens in a new tab)
Malicious Root Certificate (opens in a new tab)
Intent Spoof (opens in a new tab)
WebView Exposure (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-863Incorrect Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #17OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Aug 2026, 18:19 UTC

WeaknessesCWE-284, CWE-863

Technical details

References

Community reviews

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