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gRPC-Go: xDS RBAC and HTTP/2 Vulnerabilities

High severity GitHub Reviewed Published Jul 15, 2026 in grpc/grpc-go • Updated Jul 21, 2026

Package

gomod google.golang.org/grpc (Go)

Affected versions

< 1.82.1

Patched versions

1.82.1

Description

Multiple security vulnerabilities have been identified and addressed in grpc-go affecting the xDS RBAC authorization engine (internal/xds/rbac) and the HTTP/2 transport server implementation (internal/transport). These vulnerabilities could result in:

  • Authorization Bypass (Fail-Open) when translating xDS RBAC policies containing Metadata or RequestedServerName fields.
  • Denial of Service (High CPU Consumption) due to an HTTP/2 Rapid Reset mitigation bypass during client-initiated stream resets.
  • Denial of Service (Server Panic) when parsing crafted xDS RBAC policies containing NOT rules around unsupported fields.

Impact

What kind of vulnerability is it? Who is impacted?

xDS RBAC Authorization Bypass via Metadata & RequestedServerName matchers

  • Affected Component: xDS RBAC
  • Impact: When building policy matchers for gRPC RBAC from xDS configurations, unsupported permission and principal rules (specifically Metadata and RequestedServerName) were silently ignored and treated as no-ops.
    • If an authorization policy relied purely on these matchers for access control, treating those rules as no-ops effectively removed the restrictions.
  • If these unsupported rules were nested inside logical NOT rules (Permission_NotRule / Principal_NotId) or multi-condition OR/AND rules, silently dropping them changed the boolean logic flow of the authorization engine.

As a result, policy evaluation decisions could fail open, allowing unauthorized clients to access protected gRPC services or resources.

HTTP/2 Rapid Reset Mitigation Bypass / Denial of Service via Stream Aborts

  • Affected Component: HTTP/2 transport
  • Impact: Earlier mitigations in grpc-go for HTTP/2 Rapid Reset only applied threshold checks to items that directly resulted in control frames being written back to the wire, such as SETTINGS ACKs or server-initiated RST_STREAMs.

When a client initiated a rapid flood of stream creation (HEADERS) immediately followed by stream termination RST_STREAM, items queued up in the control buffer without counting against the transport response frame threshold. An attacker can repeatedly trigger this flood sequence to bypass reader blocking, resulting in high CPU usage, and Denial of Service (DoS).

Denial of Service (Panic) in xDS RBAC Engine via Unsupported Fields inside NOT Rules

  • Affected Component: xDS RBAC
  • Impact: The xDS RBAC policy translators recursively generate matchers for nested rules. When a NOT rule wrapped an unsupported or unhandled field (such as SourcedMetadata), the recursive step returned an empty matcher. This could result in a runtime panic when the RBAC engine attempts to authorize an incoming request.

An attacker or misconfigured/malicious xDS management server delivering an LDS/RDS update containing a NOT rule around an unhandled field causes the gRPC server process to crash immediately (CWE-248 / Denial of Service).

Patches

Has the problem been patched? What versions should users upgrade to?

All three issues have been fixed in master and will be released in 1.82.1 shortly.

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

If upgrading grpc-go immediately is not possible, apply the following workarounds based on your deployment architecture:

  • For xDS RBAC Vulnerabilities & Panics: Ensure that upstream xDS management servers do not push RBAC policies containing Metadata, RequestedServerName, or NOT rules wrapping unsupported fields (such as SourcedMetadata) to grpc-go servers.
  • For HTTP/2 Rapid Reset DOS: Configure upstream reverse proxies or load balancers (such as Envoy) with strict HTTP/2 max_concurrent_streams limits and active rate limiting on RST_STREAM frequency per connection.

Severity

Vulnerability Qualitative Severity Approximate CVSS v3.1 Score Primary Impact
xDS RBAC Authorization Bypass High 8.2 Unauthorized Access / Fail-Open
HTTP/2 Rapid Reset DOS Bypass High 7.5 High CPU Consumption / Denial of Service
xDS RBAC Engine Server Panic Medium 5.9 Process Crash / Denial of Service

References

@easwars easwars published to grpc/grpc-go Jul 15, 2026
Published to the GitHub Advisory Database Jul 21, 2026
Reviewed Jul 21, 2026
Last updated Jul 21, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

Weaknesses

Uncaught Exception

An exception is thrown from a function, but it is not caught. Learn more on MITRE.

Allocation of Resources Without Limits or Throttling

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. Learn more on MITRE.

Incorrect Authorization

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. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-hrxh-6v49-42gf

Source code

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