jsPDF is a library to generate PDFs in JavaScript. Prior to version 4.0.0, user control of the first argument of the loadFile method in the node.js build allows local file inclusion/path traversal. If given the possibility to pass unsanitized paths to the loadFile method, a user can retrieve file contents of arbitrary files in the local file system the node process is running in. The file contents are included verbatim in the generated PDFs. Other affected methods are addImage, html, and addFont. Only the node.js builds of the library are affected, namely the dist/jspdf.node.js and dist/jspdf.node.min.js files. The vulnerability has been fixed in jsPDF@4.0.0. This version restricts file system access per default. This semver-major update does not introduce other breaking changes. Some workarounds areavailable. With recent node versions, jsPDF recommends using the --permission flag in production. The feature was introduced experimentally in v20.0.0 and is stable since v22.13.0/v23.5.0/v24.0.0. For older node versions, sanitize user-provided paths before passing them to jsPDF.
Weakness
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize ‘…/…//’ (doubled triple dot slash) sequences that can resolve to a location that is outside of that directory.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Jspdf |
Parall |
* |
4.0.0 (excluding) |
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single “.” character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as “/” to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434.
- Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering “/” is insufficient protection if the filesystem also supports the use of “" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, the “…/…//” manipulation is useful for bypassing some path traversal protection schemes. If “../” sequences are removed from the “…/…//” string in a sequential fashion (as some regular expression engines and other algorithms operate) the string can collapse into the unsafe “../” value (CWE-182). Removing the first “../” yields “….//” and the second removal yields “../”.
References