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Ash has authorization bypass when bypass policy condition evaluates to true

High severity GitHub Reviewed Published Oct 17, 2025 in ash-project/ash • Updated Oct 17, 2025

Package

erlangash (Erlang)

Affected versions

>= 3.6.3, <= 3.7.0

Patched versions

3.7.1

Description

Summary

Bypass policies incorrectly authorize requests when their condition evaluates to true but their authorization checks fail and no other policies apply.

Impact

Resources with bypass policies can be accessed without proper authorization when:

  • Bypass condition evaluates to true
  • Bypass authorization checks fail
  • Other policies exist but their conditions don't match

Details

Vulnerable code in: lib/ash/policy/policy.ex:69

{%{bypass?: true},cond_expr,complete_expr},{one_condition_matches,all_policies_match}->{b(cond_exprorone_condition_matches),# <- Bug: uses condition onlyb(complete_exprorall_policies_match)}

The final authorization decision is: one_condition_matches AND all_policies_match

When a bypass condition is true but bypass policies fail, and subsequent policies have non-matching conditions:

  1. one_condition_matches = cond_expr (bypass condition) = true (bug - should check if bypass actually authorizes)
  2. all_policies_match = (complete_expr OR NOT cond_expr) for each policy
    • For non-matching policies: (false OR NOT false) = true (policies don't apply)
  3. Final: true AND true = true (incorrectly authorized)

The bypass condition alone satisfies "at least one policy applies" even though the bypass fails to authorize.

Fix

Replace cond_expr with complete_expr on line 69:

{%{bypass?: true},_cond_expr,complete_expr},{one_condition_matches,all_policies_match}->{b(complete_exprorone_condition_matches),# <- Fixedb(complete_exprorall_policies_match)}

Line 52 should also be updated for consistency (though it's only triggered when bypass is the last policy, making it coincidentally safe in practice):

{%{bypass?: true},_cond_expr,complete_expr},{one_condition_matches,true}->{b(complete_exprorone_condition_matches),# <- For consistencycomplete_expr}

PoC

policiesdobypassalways()doauthorize_ifactor_attribute_equals(:is_admin,true)endpolicyaction_type(:read)doauthorize_ifalways()endend

Non-admin user can perform create actions (should be denied).

Test demonstrating the bug:

test"bypass policy bug"dopolicies=[%Ash.Policy.Policy{bypass?: true,condition: [{Ash.Policy.Check.Static,result: true}],# condition = truepolicies: [%Ash.Policy.Check{type: :authorize_if,check: {Ash.Policy.Check.Static,result: false},# policies = falsecheck_module: Ash.Policy.Check.Static,check_opts: [result: false]}]},%Ash.Policy.Policy{bypass?: false,condition: [{Ash.Policy.Check.Static,result: false}],policies: [%Ash.Policy.Check{type: :authorize_if,check: {Ash.Policy.Check.Static,result: true},check_module: Ash.Policy.Check.Static,check_opts: [result: true]}]}]expression=Ash.Policy.Policy.expression(policies,%{})assertexpression==false# Expected: false (deny)# Actual on main: true (incorrectly authorized)end

References

@zachdanielzachdaniel published to ash-project/ash Oct 17, 2025
Published by the National Vulnerability DatabaseOct 17, 2025
Published to the GitHub Advisory Database Oct 17, 2025
Reviewed Oct 17, 2025
Last updated Oct 17, 2025

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 Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability None
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:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(29th percentile)

Weaknesses

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

CVE-2025-48044

GHSA ID

GHSA-pcxq-fjp3-r752

Source code

Credits

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