|
|
|
|
CWE-61: UNIX Symbolic Link (Symlink) Following | |
| | UNIX Symbolic Link (Symlink) Following |
Definition in a New Window 
|
| Compound Element ID: 61 (Compound Element Variant: Composite) | | Status: Incomplete |
 Description
Description Summary The software, when opening a file or directory, does not
sufficiently account for when the file is a symbolic link that resolves to a
target outside of the intended control sphere. This could allow an attacker to
cause the software to operate on unauthorized files.
Extended Description
A software system that allows UNIX symbolic links (symlink) as part of
paths whether in internal code or through user input can allow an attacker
to spoof the symbolic link and traverse the file system to unintended
locations or access arbitrary files. The symbolic link can permit an
attacker to read/write/corrupt a file that they originally did not have
permissions to access.
Alternate Terms
| Symlink following | |
|---|
| symlink vulnerability | |
|---|
Time of Introduction Likelihood of Exploit Observed Examples Potential Mitigations | Phase | Description |
|---|
| Symbolic link attacks often occur when a program creates a tmp
directory that stores files/links. Access to the directory should be
restricted to the program as to prevent attackers from manipulating the
files. |
| Follow the principle of least privilege when assigning access rights
to files. Denying access to a file can prevent an attacker from
replacing that file with a link to a sensitive file. Ensure good
compartmentalization in the system to provide protected areas that can
be trusted. |
Other Notes
|
Fault: filename predictability, insecure directory permissions, non-atomic
operations, race condition.
These are typically reported for temporary files or privileged
programs.
|
Weakness Ordinalities | Ordinality | Description |
|---|
Resultant | (where the
weakness is typically related to the presence of some other
weaknesses) |
Relationships Research Gaps
|
Symlink vulnerabilities are regularly found in C and shell programs, but
all programming languages can have this problem. Even shell programs are
probably under-reported.
"Second-order symlink vulnerabilities" may exist in programs that invoke
other programs that follow symlinks. They are rarely reported but are likely
to be fairly common when process invocation is used. Reference:
[Christey2005]
|
Causal Nature Taxonomy Mappings | Mapped Taxonomy Name | Node ID | Fit | Mapped Node Name |
|---|
| PLOVER | | | UNIX symbolic link following |
References Content History | Submissions |
|---|
| Submission Date | Submitter | Organization | Source |
|---|
| PLOVER | | Externally Mined | | | Modifications |
|---|
| Modification Date | Modifier | Organization | Source |
|---|
| 2008-07-01 | Eric Dalci | Cigital | External | | updated Time of Introduction | | 2008-09-08 | CWE Content Team | MITRE | Internal | | updated Relationships, Observed Example, Other Notes,
Research Gaps, Taxonomy Mappings,
Weakness Ordinalities | | 2008-10-14 | CWE Content Team | MITRE | Internal | | updated Description | | 2009-07-27 | CWE Content Team | MITRE | Internal | | updated Observed Examples |
|
