RHSA-2026:18480

Improper Input Validation vulnerability in qs (parse modules) allows HTTP DoS.This issue affects qs: < 6.14.1. Summary The arrayLimit option in qs did not enforce limits for bracket notation (a[]=1&a[]=2), only for indexed notation (a[0]=1). This is a consistency bug; arrayLimit should apply uniformly across all array notations. Note: The default parameterLimit of 1000 effectively mitigates the DoS scenario originally described. With default options, bracket notation cannot produce arrays larger than parameterLimit regardless of arrayLimit, because each a[]=valueconsumes one parameter slot. The severity has been reduced accordingly. Details The arrayLimit option only checked limits for indexed notation (a[0]=1&a[1]=2) but did not enforce it for bracket notation (a[]=1&a[]=2). Vulnerable code (lib/parse.js:159-162): if (root === '[]' && options.parseArrays) { obj = utils.combine([], leaf); // No arrayLimit check } Working code (lib/parse.js:175): else if (index <= options.arrayLimit) { // Limit checked here obj = []; obj[index] = leaf; } The bracket notation handler at line 159 uses utils.combine([], leaf) without validating against options.arrayLimit, while indexed notation at line 175 checks index <= options.arrayLimit before creating arrays. PoC const qs = require('qs'); const result = qs.parse('a[]=1&a[]=2&a[]=3&a[]=4&a[]=5&a[]=6', { arrayLimit: 5 }); console.log(result.a.length); // Output: 6 (should be max 5) Note on parameterLimit interaction: The original advisory's "DoS demonstration" claimed a length of 10,000, but parameterLimit (default: 1000) caps parsing to 1,000 parameters. With default options, the actual output is 1,000, not 10,000. Impact Consistency bug in arrayLimit enforcement. With default parameterLimit, the practical DoS risk is negligible since parameterLimit already caps the total number of parsed parameters (and thus array elements from bracket notation). The risk increases only when parameterLimit is explicitly set to a very high value.

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.

node-tar,a Tar for Node.js, contains a vulnerability in versions prior to 7.5.7 where the security check for hardlink entries uses different path resolution semantics than the actual hardlink creation logic. This mismatch allows an attacker to craft a malicious TAR archive that bypasses path traversal protections and creates hardlinks to arbitrary files outside the extraction directory. Version 7.5.7 contains a fix for the issue.

node-tar is a Tar for Node.js. The node-tar library (<= 7.5.2) fails to sanitize the linkpath of Link (hardlink) and SymbolicLink entries when preservePaths is false (the default secure behavior). This allows malicious archives to bypass the extraction root restriction, leading to Arbitrary File Overwrite via hardlinks and Symlink Poisoning via absolute symlink targets. This vulnerability is fixed in 7.5.3.