Executive Summary
IBM has disclosed CVE-2026-15435, a critical path traversal vulnerability in IBM App Connect Enterprise (ACE). With a CVSS 3.1 score of 9.8, this is among the highest-severity vulnerabilities of its class. A remote, unauthenticated attacker can send a specially crafted URL containing /../ (dot-dot) sequences to write arbitrary files anywhere on the system — enabling remote code execution, configuration tampering, or full server compromise.
Both the v12 and v13 branches of IBM App Connect Enterprise are affected across a wide range of versions. The vulnerability was published to the NVD on July 30, 2026.
Vulnerability Details
| Field | Value |
|---|---|
| CVE ID | CVE-2026-15435 |
| CVSS 3.1 Score | 9.8 (Critical) |
| CWE | CWE-22 — Improper Limitation of a Pathname to a Restricted Directory (Path Traversal) |
| Attack Vector | Network |
| Attack Complexity | Low |
| Privileges Required | None |
| User Interaction | None |
| Scope | Unchanged |
| Impact | High Confidentiality / High Integrity / High Availability |
How It Works
The vulnerability stems from insufficient validation of URL path components in IBM App Connect Enterprise's HTTP request handling layer. An attacker can send requests with /../ sequences — commonly called "dot-dot slash" or directory traversal sequences — which the server fails to properly canonicalize or restrict.
By chaining multiple traversal sequences in a specially crafted URL, an attacker can:
- Escape the web root and navigate to arbitrary filesystem locations
- Write attacker-controlled content to critical system files — including web shells, configuration overrides, or malicious binaries
- Achieve remote code execution by writing a web shell or overwriting executable files
Because no authentication is required (CVSS PR:N, UI:N), this vulnerability can be exploited by any network-adjacent or internet-facing attacker with access to the ACE endpoint.
Affected Products
| Product | Affected Versions |
|---|---|
| IBM App Connect Enterprise | 13.0.1.0 through 13.0.7.2 |
| IBM App Connect Enterprise | 12.0.1.0 through 12.0.12.27 |
Organizations running ACE in hybrid integration environments, cloud-native pipelines, or as a public-facing API gateway are at elevated risk given the unauthenticated, network-exploitable nature of this flaw.
Remediation
Consult the IBM security bulletin associated with CVE-2026-15435 for official fix information and patch availability. General guidance for IBM App Connect Enterprise path traversal vulnerabilities:
- Apply the latest Fix Pack — upgrade to a version beyond the listed affected ranges
- Apply interim fixes where available through IBM Fix Central while awaiting the next full Fix Pack
- Restrict network access to ACE administrative and integration endpoints using firewall rules, network segmentation, or API gateway controls
- Deploy WAF rules with path traversal detection patterns (block URLs containing
../,%2e%2e%2f,%2e%2e/,..%2f, etc.) - Monitor filesystem integrity using FIM (File Integrity Monitoring) to detect unexpected file writes
Mitigation Until Patched
If patching cannot be applied immediately:
- Block external access to IBM ACE HTTP endpoints at the perimeter firewall — restrict to known internal IP ranges only
- Enable URL normalization on your load balancer or reverse proxy to strip traversal sequences before they reach ACE
- Audit recent access logs for URL patterns containing
%2e,%2f,.., or excessive path depth — these may indicate active exploitation attempts - Run ACE with least-privilege OS accounts to limit the filesystem locations an arbitrary write could reach