Automated code analysis techniques might not be able to reliably detect this weakness, since the application's behavior and general security model dictate which resource locks are critical. Interpretation of the weakness might require knowledge of the environment, e.g. if the existence of a file is used as a lock, but the file is created in a world-writable directory.
CWE-412 Base Incomplete
Unrestricted Externally Accessible Lock
This vulnerability occurs when a system correctly checks for a lock's existence, but an unauthorized external actor can control or influence that lock.
Definition
What is CWE-412?
This vulnerability occurs when a system correctly checks for a lock's existence, but an unauthorized external actor can control or influence that lock.
When an attacker can manipulate a lock—such as a mutex, file lock, or a shared resource used as a lock—they can prevent the application from accessing critical resources or performing essential operations. This effectively creates a denial-of-service condition, as the system remains blocked waiting for a lock it cannot acquire.
The severity of this issue escalates if the attacker can hold the lock indefinitely, leading to a permanent disruption of service. Developers must ensure that lock mechanisms are secured within the application's trusted boundary and cannot be created, modified, or sustained by untrusted external sources.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-412
-
Program can not execute when attacker obtains a mutex.
-
Program can not execute when attacker obtains a lock on a critical output file.
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Program can not execute when attacker obtains a lock on a critical output file.
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Critical file can be opened with exclusive read access by user, preventing application of security policy. Possibly related to improper permissions, large-window race condition.
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Chain: predictable file names used for locking, allowing attacker to create the lock beforehand. Resultant from permissions and randomness.
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Chain: Lock files with predictable names. Resultant from randomness.
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Product does not check if it can write to a log file, allowing attackers to avoid logging by accessing the file using an exclusive lock. Overlaps unchecked error condition. This is not quite CWE-412, but close.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
Identifiziere einen Codepfad, der nicht vertrauenswürdige Eingaben ohne Validierung verarbeitet.
- 2
Erzeuge eine Payload, die das unsichere Verhalten auslöst — Injection, Traversal, Overflow oder Logik-Missbrauch.
- 3
Liefere die Payload über einen normalen Request aus und beobachte die Reaktion der Anwendung.
- 4
Iteriere, bis die Antwort Daten preisgibt, Angreifer-Code ausführt oder Berechtigungen eskaliert.
Verwundbares Codebeispiel
Vulnerable PHP
This code tries to obtain a lock for a file, then writes to it.
function writeToLog($message){
$logfile = fopen("logFile.log", "a");
```
//attempt to get logfile lock*
if (flock($logfile, LOCK_EX)) {
```
fwrite($logfile,$message);
```
// unlock logfile*
flock($logfile, LOCK_UN);}
else {
```
print "Could not obtain lock on logFile.log, message not recorded\n";
}
}
fclose($logFile); Sicheres Codebeispiel
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Präventions-Checkliste
How to prevent CWE-412
- Architecture and Design / Implementation Use any access control that is offered by the functionality that is offering the lock.
- Architecture and Design / Implementation Use unpredictable names or identifiers for the locks. This might not always be possible or feasible.
- Architecture and Design Consider modifying your code to use non-blocking synchronization methods.
Erkennungssignale
How to detect CWE-412
CWE-412
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Häufig gestellte Fragen Was ist CWE-412?
Wie gravierend ist CWE-412?
Welche Sprachen oder Plattformen sind von CWE-412 betroffen?
Wie kann ich CWE-412 verhindern?
Wie erkennt und behebt Plexicus CWE-412?
Wo erfahre ich mehr über CWE-412?
Frequently asked questions
Was ist CWE-412?
This vulnerability occurs when a system correctly checks for a lock's existence, but an unauthorized external actor can control or influence that lock.
Wie gravierend ist CWE-412?
MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.
Welche Sprachen oder Plattformen sind von CWE-412 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-412 verhindern?
Use any access control that is offered by the functionality that is offering the lock. Use unpredictable names or identifiers for the locks. This might not always be possible or feasible.
Wie erkennt und behebt Plexicus CWE-412?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-412 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.
Wo erfahre ich mehr über CWE-412?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/412.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-412
CWE-667 Parent
Improper Locking
This vulnerability occurs when a program fails to correctly acquire or release a lock on a shared resource, such as a file, database…
CWE-1232 Sibling
Improper Lock Behavior After Power State Transition
This vulnerability occurs when a hardware lock bit, designed to protect critical system configuration registers, is improperly reset or…
CWE-1233 Sibling
Security-Sensitive Hardware Controls with Missing Lock Bit Protection
This vulnerability occurs when a hardware device uses a lock bit to protect critical configuration registers, but the lock fails to…
CWE-1234 Sibling
Hardware Internal or Debug Modes Allow Override of Locks
Hardware debug modes or internal states can bypass critical system lock protections, allowing unauthorized changes to device configuration.
CWE-413 Sibling
Improper Resource Locking
This vulnerability occurs when an application fails to properly lock a shared resource, such as a file or memory location, before…
CWE-414 Sibling
Missing Lock Check
This vulnerability occurs when software fails to verify that a proper synchronization lock is active before accessing or modifying a…
CWE-609 Sibling
Double-Checked Locking
Double-checked locking is an insufficient synchronization pattern where a program checks a resource's state, acquires a lock, and checks…
CWE-764 Sibling
Multiple Locks of a Critical Resource
This vulnerability occurs when a critical resource, such as a file, data structure, or connection, is locked more times than the software…
CWE-765 Sibling
Multiple Unlocks of a Critical Resource
This vulnerability occurs when a critical resource, like a lock or semaphore, is unlocked more times than it was locked, putting the…
Ressourcen
Further reading
Bereit, das Wesentliche zu validieren?
Bereit zu validieren, was zählt.
Plexicus ist Proof-Driven AppSec: validierte Funde, kontextuelles Verständnis und geprüfte Remediation — in Evidenz verankert, mit Ihnen gescoped.