CVE-2026-23950 node-tar has Race Condition in Path Reservations via Unicode Ligature Collisions on macOS APFS
An attacker can exploit a race condition in node-tar on macOS to bypass path locks and overwrite arbitrary files via symlink poisoning.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-23950?
CVE-2026-23950 is a high-severity vulnerability in isaacs node-tar, published on 20 Jan 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
node-tar,a Tar for Node.js, has a race condition vulnerability in versions up to and including 7.5.3. This is due to an incomplete handling of Unicode path collisions in the `path-reservations` system. On case-insensitive or normalization-insensitive filesystems (such as macOS APFS, In which it has been tested), the library fails to lock colliding paths (e.g., `ß` and `ss`), allowing them to be processed in parallel. This bypasses the library's internal concurrency safeguards and permits Symlink Poisoning attacks via race conditions. The library uses a `PathReservations` system to ensure that metadata checks and file operations for the same path are serialized. This prevents race conditions where one entry might clobber another concurrently. This is a Race Condition which enables Arbitrary File Overwrite. This vulnerability affects users and systems using node-tar on macOS (APFS/HFS+). Because of using `NFD` Unicode normalization (in which `ß` and `ss` are different), conflicting paths do not have their order properly preserved under filesystems that ignore Unicode normalization (e.g., APFS (in which `ß` causes an inode collision with `ss`)). This enables an attacker to circumvent internal parallelization locks (`PathReservations`) using conflicting filenames within a malicious tar archive. The patch in version 7.5.4 updates `path-reservations.js` to use a normalization form that matches the target filesystem's behavior (e.g., `NFKD`), followed by first `toLocaleLowerCase('en')` and then `toLocaleUpperCase('en')`. As a workaround, users who cannot upgrade promptly, and who are programmatically using `node-tar` to extract arbitrary tarball data should filter out all `SymbolicLink` entries (as npm does) to defend against arbitrary file writes via this file system entry name collision issue.
Which versions are affected by CVE-2026-23950?
2 open source packages ship an affected version, including tar. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
tar npm | All versions | 7.5.4 |
tar npm | All versions | 7.5.4 |
Products include Isaacs Tar.
How do I fix CVE-2026-23950?
Upgrade tar to 7.5.4 or later.
Is CVE-2026-23950 being exploited?
There is no known exploitation of CVE-2026-23950 in the wild and no public exploit code.
Other vulnerabilities in isaacs node-tar
- CVE-2026-59873 node-tar: Decompression/parse DoS via unlimited input
- CVE-2026-59874 node-tar: Negative tar entry size causes infinite loop in archive replace
- CVE-2026-31802 node-tar Symlink Path Traversal via Drive-Relative Linkpath
- CVE-2026-29786 node-tar: Hardlink Path Traversal via Drive-Relative Linkpath
- CVE-2026-24842 node-tar Vulnerable to Arbitrary File Creation/Overwrite via Hardlink Path Traversal
Sources
Also known as CLEANSTART-2026-UO17156, CLEANSTART-2026-VN06926, DEBIAN-CVE-2026-23950, ECHO-f4de-fc09-5377, GHSA-r6q2-hw4h-h46w, MINI-3hc2-w3hh-2gvw and 23 more.