CWE-775: Missing Release of File Descriptor or Handle after Effective Lifetime
Missing Release of File Descriptor or Handle after Effective Lifetime
Weakness ID: 775 (Weakness Variant)
Status: Incomplete
Description
Description Summary
The software does not release a file descriptor or handle after
its effective lifetime has ended, i.e., after the file descriptor/handle is no
longer needed.
Extended Description
When a file descriptor or handle is not released after use (typically by
explicitly closing it), attackers can cause a denial of service by consuming
all available file descriptors/handles, or otherwise preventing other system
processes from obtaining their own file descriptors/handles.
Time of Introduction
Implementation
Common Consequences
Scope
Effect
Availability
When allocating resources without limits, an attacker could prevent
all other processes from accessing the same type of resource.
Likelihood of Exploit
Medium to High
Potential Mitigations
Phase
Description
Implementation
For system resources, consider using the getrlimit() function included
in the sys/resources library in order to determine how many resources
are currently allowed to be opened for the process.
When the current levels get close to the maximum that is defined for
the application (see CWE-770), then limit the allocation of further
resources to privileged users; alternately, begin releasing resources
for less-privileged users. While this mitigation may protect the system
from attack, it will not necessarily stop attackers from adversely
impacting other users.
(Good Code)
C
#include <sys/resource.h>
...
int return_value;
struct rlimit rlp;
...
return_value = getrlimit(RLIMIT_NOFILE, &rlp);
Operation
Use resource-limiting settings provided by the operating system or
environment. For example, setrlimit() can be used to set limits for
certain types of resources. However, this is not available on all
operating systems.
Ensure that your application performs the appropriate error checks and
error handling in case resources become unavailable (CWE-703).
Vulnerability theory is largely about how behaviors and resources
interact. "Resource exhaustion" can be regarded as either a consequence or
an attack, depending on the perspective. This entry is an attempt to reflect
one of the underlying weaknesses that enable these attacks (or consequences)
to take place.
Description
