CVE-2026-82744 in Ash
Summary
by MITRE • 09/01/2026
Not Failing Securely (Failing Open) vulnerability in ash-project ash skips an Ash.Reactor change when the guard controlling it raises, so a change meant to run does not.
An Ash.Reactor change step can be gated by where validations that decide whether the change runs. Ash.Reactor.ChangeStep (lib/ash/reactor/steps/change_step.ex) evaluated those guards in apply_where_clauses/3, and apply_validation rescued any exception into {:error, error}. The reduce treated that identically to a guard whose condition was simply not met and bypassed the change. So when a guard raises (for example on attacker-influenced input), a change that enforces a security-relevant modification is skipped rather than failing the step. The fix distinguishes a raised exception (now {:raised, error}) and halts the step with an error, failing closed.
This issue affects ash: from 3.0.0-rc.17 before 3.32.2.
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Analysis
by VulDB Data Team • 09/01/2026
The vulnerability identified in the Ash framework represents a critical failure to handle exceptions securely during the execution of reactor changes. Specifically, this is an instance of failing open rather than failing closed, where the system continues operation despite encountering an error condition that should have halted processing. In the context of ash-project ash versions ranging from 3.0.0-rc.17 up to but not including 3.32.2, the core issue resides within the Ash.Reactor.ChangeStep module. This component is responsible for evaluating guard clauses and validations that determine whether a specific change step should be executed. The flaw occurs in the apply_where_clauses/3 function, which processes these guards. When an exception is raised during this evaluation process, typically due to malformed or attacker-influenced input triggering unexpected behavior within validation logic, the code rescues the error and converts it into an {:error, error} tuple.
The operational impact of this design choice is severe because the subsequent reduce function treats the rescued {:error, error} state identically to a scenario where a guard condition simply evaluates to false. In normal operation, if a guard returns false, the change step is correctly bypassed as intended by the application logic. However, when an exception occurs due to malicious input or internal errors, treating it as a simple non-matching guard means that security-relevant modifications are silently skipped rather than causing the entire transaction or action to fail. This allows potentially harmful data to pass through validation layers without triggering the necessary enforcement mechanisms designed to protect system integrity. For example, if a change step is responsible for sanitizing input or enforcing access controls, and an exception prevents its execution due to this bug, those protections are effectively disabled for that specific operation.
From a technical classification perspective, this vulnerability aligns with CWE-254, which describes the improper handling of exceptions resulting in failure to secure resources or operations. It also relates closely to CWE-755, concerning improper handling of unexpected input data, as the root cause often involves unanticipated error states triggered by external inputs. In terms of attack vectors and techniques, this behavior can be leveraged within the ATT&CK framework under T1068 Exploitation for Privilege Escalation or T1190 Exploit Public-Facing Application if the vulnerability allows an attacker to bypass security controls in a web-facing service. The ability to cause a validation failure that results in silent skipping of critical logic provides an avenue for privilege escalation or data integrity compromise, depending on what specific changes are gated by these guards.
The resolution implemented in version 3.32.2 addresses this flaw by distinguishing between a guard condition that simply does not match and one where an exception has been raised. The updated code now returns {:raised, error} when an exception occurs during the evaluation of guards or validations. This distinct state is recognized by the reduce function as a fatal error rather than a benign non-match, causing it to halt the step immediately with an error. By failing closed in these scenarios, the framework ensures that any unexpected condition prevents further execution until the issue can be addressed, thereby maintaining the integrity of security controls and preventing silent bypasses. This change enforces strict adherence to secure coding principles where errors must result in safe failure modes rather than continuing operation under potentially compromised conditions.
To mitigate this vulnerability for systems still running affected versions, immediate upgrading to ash version 3.32.2 or later is required. For organizations unable to upgrade immediately due to dependency constraints, implementing custom middleware or wrapper logic around Ash.Reactor.ChangeStep calls may provide a temporary workaround by explicitly checking for error states that might indicate exceptions rather than simple guard failures. However, such workarounds are not recommended as primary solutions because they require deep understanding of the internal state machine and risk introducing new bugs. Security teams should also audit their application logs for unusual patterns where validation steps appear to have been skipped without explicit logical reasons, which could indicate exploitation attempts against this flaw. Regular security assessments focusing on input validation paths within reactor-based workflows are essential to detect any residual risks or similar implementation errors in custom extensions of the Ash framework.