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Atomicorp WAF Research Note: CVE-2026-77956

EEx template evaluation of prompt content in AshAi enables remote code execution

CVE Details

Status: Attack Blocked by Atomicorp
  • Already protected by existing Atomicorp WAF rules
  • Protection status: Understanding Atomicorp WAF Protection Status
  • CVE: CVE-2026-77956
  • Name: EEx template evaluation of prompt content in AshAi enables remote code execution
  • Severity: High
  • CVSS: 8.9 (v4.0) (High)
  • CVSS version: 4.0
  • CVSS source: EEF CNA
  • CVSS vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
    • Attack vector: Local
    • Attack complexity: Low
    • Attack requirements: Present
    • Privileges required: None
    • User interaction: None
    • Vulnerable-system confidentiality: High
    • Vulnerable-system integrity: High
    • Vulnerable-system availability: High
    • Subsequent-system confidentiality: High
    • Subsequent-system integrity: High
    • Subsequent-system availability: High
    • Scope: X
  • CWE: CWE-94 — Improper Control of Generation of Code (‘Code Injection’)
  • Related CAPEC attack patterns (via MITRE CWE relationships): CAPEC-242 , CAPEC-35 , CAPEC-77
  • Vendor: ash-project
  • Vulnerable product: ash ai
  • CVE published: 2026-08-31
  • CVE last modified: 2026-09-01
  • EPSS: 0.0019; 9.3th percentile (FIRST )
  • Latest Update: 2026-09-06
  • Selected Rule IDs observed: 340014 , 344361 , 344363 , 344364 , 344366 , 344370
  • Matching rules: 6; rules with blocking actions: 6
  • Would-block Rule IDs: 340014 , 344361 , 344363 , 344364 , 344366 , 344370
  • Request surfaces inspected: JSON request data, Request argument names, Request arguments, Request cookies, SOAP request data, XML request data

Vulnerability Description

Improper Control of Generation of Code (Code Injection) vulnerability in ash-project ash_ai allows a remote, unauthenticated client to execute arbitrary Elixir code.

AshAi.Actions.Prompt evaluates prompt content through EEx.eval_string/2. The documented prompt: fn input, context -> … end form lets the prompt content be built from action arguments, so when a prompt action’s text incorporates request data, that attacker-controlled text is compiled and run as an EEx template (Elixir source). Content such as <%= System.cmd(…) %> therefore executes on the server before any model request is made, requiring no authentication beyond reaching a prompt action. The fix stops evaluating function-supplied prompt content as EEx; only statically configured templates are evaluated.

This issue affects ash_ai: from 0.1.0 before 1.0.0.

  1. Maintain the observed Atomicorp protections. Keep your Atomicorp commercial rules current and confirm that the selected observed rules (340014 , 344361 , 344363 , 344364 , 344366 , 344370 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

  2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

    • Affected versions: ash-project ash_ai versions earlier than 1.0.0.
    • Affected versions: ash-project ash_ai versions earlier than e9948254b5659c1143b73dc2f59f457931e64514.
    • Recommended upgrade: Upgrade ash-project ash_ai to 1.0.0 or later.
    • Recommended upgrade: Upgrade ash-project ash_ai to e9948254b5659c1143b73dc2f59f457931e64514 or later.

  3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

Test or Research Source

  • Source: Atomicorp AI Research Framework
  • Tags: cve, derived, rce, waf-probe

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

  • Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
  • Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
  • Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
  • Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
  • Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ .