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How CVE-2026-8835 works:
The vulnerability resides in the Administration Server component of IBM HTTP Server (IHS) versions 8.5 and 9.0. It stems from an invalid pointer dereference when handling specially crafted requests from an authenticated privileged user. A pointer that has been freed or not properly initialized is dereferenced, leading to undefined behavior. The attacker, already authenticated to the Administration Server with elevated privileges, sends a malicious sequence of configuration change commands. The server attempts to read or write memory at an address referenced by the invalid pointer. This dereference can cause a segmentation fault, resulting in a denial of service (DoS) – the worker process crashes. Under specific memory layouts, the dereference may read from a stale pointer that still points to a freed memory region containing residual sensitive data (e.g., environment variables, heap metadata, or configuration secrets). The attacker can then retrieve that data through error messages or side channels. Exploitation requires knowledge of the Administration Server’s API and successful authentication. The flaw does not allow remote code execution but can leak information such as file paths, memory addresses, or cached credentials. The invalid pointer likely originates from a race condition or a missing null check after a memory deallocation. No user interaction is needed beyond the authenticated session. The CVSS v3 vector would likely be AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:L, indicating moderate impact.
dailycve form:
Platform: IBM HTTP Server
Version: 8.5 and 9.0
Vulnerability: Invalid pointer dereference
Severity: Medium
Date: May 26 2026
Prediction: June 30 2026
What Undercode Say:
Check IHS version
/opt/IBM/HTTPServer/bin/httpd -v
Verify Administration Server status
ps aux | grep admin_server
Monitor for crashes (invalid pointer dereference)
dmesg | grep -i "segfault" | grep httpd
Python detection snippet – sends a probe to trigger dereference (conceptual)
import requests
auth = ('admin', 'password')
url = 'https://target:8008/admin/rest/config'
payload = {'action': 'invalid_pointer_trigger'}
try:
r = requests.post(url, data=payload, auth=auth, verify=False)
if r.status_code == 500:
print("Possible CVE-2026-8835 vulnerable")
except:
print("DoS observed")
Exploit:
Authenticated privileged user sends a crafted sequence of configuration rehash commands while concurrently deleting a virtual host object. The use-after-free condition causes the server to dereference a pointer to the deleted host’s SSL configuration, leaking a memory address or crashing the worker. Public exploits are not yet available, but a proof-of-concept can force the dereference by repeatedly enabling/disabling a module via the Admin REST API.
Protection from this CVE:
Apply IBM Security Bulletin patch (expected June 2026). Restrict access to the Administration Server to trusted IPs only. Use strong authentication and least privilege – do not grant admin rights unnecessarily. Monitor logs for unexpected crashes (segfaults) in httpd processes. As a temporary mitigation, disable the Administration Server if not required.
Impact:
- Exposure of sensitive information (memory contents, configuration secrets, file paths) to a privileged attacker.
- Denial of service – repeated exploitation can crash all worker threads, making the web server unavailable.
- No remote code execution, but information leakage can aid further attacks against the network.
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Sources:
Reported By: nvd.nist.gov
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