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VCID-58kk-kzpt-m7ez
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exiftool-vendored vulnerable to argument injection via newline characters in tag names
### Impact
`exiftool-vendored` starts ExifTool in `-stay_open True -@ -` mode, where arguments are read from stdin one per line. In affected versions, several caller-supplied strings were interpolated into ExifTool arguments without rejecting line delimiters. A newline or carriage return inside one of those strings could split a single intended argument into multiple ExifTool arguments, allowing argument injection. The fix also rejects NUL bytes as unsafe control characters.
Applications that pass attacker-controlled strings to affected APIs may allow an attacker to make ExifTool read files accessible to the ExifTool process, or write output to attacker-chosen file system paths accessible to that process. No remote code execution has been demonstrated.
The reported write-path issue is caused by unsanitized tag **keys**. Tag **values** passed to `ExifTool#write` are not affected, because `WriteTask` already encodes whitespace characters in values (e.g. `\n` -> ` `) before transmission.
Confirmed affected inputs:
- **Tag-name arguments / tag keys** — keys of the `tags` object passed to `ExifTool#write`; entries of the `retain` option to `ExifTool#deleteAllTags`; entries of the `numericTags` option to `ExifTool#read`; the `tagname` argument to `ExifTool#extractBinaryTag` and `#extractBinaryTagToBuffer`.
- **Filename / path arguments** to `ExifTool#write`, `#read`, `#readRaw`, `#deleteAllTags`, `#rewriteAllTags`, `#extractBinaryTag`, `#extractBinaryTagToBuffer`, and the binary-extraction convenience methods `#extractJpgFromRaw`, `#extractPreview`, and `#extractThumbnail`. `path.resolve()` does not strip newlines, so an application that accepts attacker-controlled filenames containing newline characters was vulnerable.
- **The `imageHashType` option** to `ExifTool#read`. TypeScript types restrict this to a literal union, but JS callers or callers with weakened type checking could reach the sink.
Applications that only pass hardcoded strings for tag names, options, and filenames are not affected.
### Patches
Fixed in **v35.19.0**. Two layers of defense:
1. **Per-site input validation.** A new `validateTagName` helper rejects any tag-name string containing characters outside the ExifTool tag grammar (letters, digits, `:`, `-`, `_`, and the ExifTool modifiers `*`, `?`, `+`, `#`). Applied at every tag-name interpolation site.
2. **Defense-in-depth at the command renderer.** `ExifToolTask.renderCommand` now rejects _any_ argument containing `\r`, `\n`, or `\0` before it is sent to the ExifTool process. This catches injection via filename arguments, option values, and any future interpolation site that forgets the per-site validator.
### Workarounds
Upgrade to v35.19.0 or later.
If upgrading immediately is not possible, reject untrusted strings containing control characters before passing them to the affected APIs. Conservative guard:
```ts
function assertSafeForExifTool(s: string): void {
if (typeof s !== "string" || /[\x00-\x20=<>]/.test(s)) {
throw new Error("Rejected unsafe string for ExifTool");
}
}
```
Apply to tag names, `retain` / `numericTags` entries, binary-extraction tag names, filenames, and the `imageHashType` option. This is a denylist and is strictly weaker than the library's internal validator; it is sufficient to block the known PoCs but will accept strings that the library itself now rejects.
### Resources
- ExifTool `-stay_open` / argument-file documentation: https://exiftool.org/exiftool_pod.html#stay_open-FLAG
- ExifTool tag-name reference: https://exiftool.org/TagNames/
- CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection') — https://cwe.mitre.org/data/definitions/88.html
### Credit
- Reporter: Hank Tam
- Affiliation: Independent
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CVE-2026-43893
GHSA-cw26-7653-2rp5
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