CVE-2026-33750

A vulnerability was found in the brace-expansion library up to versions 1.1.11, 2.0.1, 3.0.0, and 4.0.0, involving inefficient regular expression complexity in the expand function in index.js. The attack can be launched remotely.

The brace-expansion library generates arbitrary strings containing a common prefix and suffix. Prior to 1.1.20, 2.1.6, 3.0.8, and 5.0.11, deeply nested brace groups cause expand_() to recurse once per nesting level at comma-member and single-set expansion sites, exhausting the native stack before output limits can apply and potentially terminating the Node.js process. expand_ performs uncontrolled recursion for nested brace alternatives and single-part sets. deeply nested brace groups supplied as an untrusted pattern. expand_ is affected. expand is affected. Comma members is affected. Single set is affected. native stack exhaustion during nested sub-expansion. process-terminating denial of service. This issue is fixed in versions 1.1.20, 2.1.6, 3.0.8, and 5.0.11.

The brace-expansion library generates arbitrary strings containing a common prefix and suffix. Prior to 1.1.21, 2.1.7, 3.0.9, and 5.0.12, the expand function handles untrusted {a},b}-shaped patterns with many trailing closing braces by restarting its scan once for each trailing closing brace. The successive full-input rescans with linear working-string growth cause quadratic CPU time and memory pressure that can block the Node.js event loop. The process eventually recovers, making the impact a recoverable CPU denial of service.

The brace-expansion library generates arbitrary strings containing a common prefix and suffix. Prior to 1.1.19, 2.1.5, 3.0.7, and 5.0.10, crafted brace patterns can exhaust the native stack in parseCommaParts because it recursively processes the remainder once per brace group and uses push.apply to pass every element of a very large comma-part array as a function argument. This can terminate the Node.js process in a process-terminating denial of service.

The brace-expansion library prior to versions 1.1.18, 2.1.4, 3.0.6, and 5.0.9 contains a vulnerability where the expand() function does not apply maxLength while constructing comma-alternative intermediate arrays or padded sequences. This allows attacker-controlled input to exhaust memory or block the event loop.

brace-expansion through 5.0.7 is vulnerable to denial of service via memory exhaustion. The expand() function limits the number of results with a max option (default 100,000) but does not bound the length of each result string. By chaining multiple brace groups, an attacker keeps the result count under the limit while making each result progressively longer, so total memory scales until the process hits a fatal out-of-memory error. About 7.5 KB of input ('{a,b}'.repeat(1500)) crashes a default Node.js process. Fixed in 5.0.8 by adding a maxLength option (default 4,000,000).

A vulnerability in brace-expansion up to version 5.0.6 allows a DoS attack by sending a crafted string with many consecutive non-expanding '{}' brace groups. The expand() function has exponential time complexity, causing high CPU consumption and event-loop blocking.

The brace-expansion library versions 5.0.0 to before 5.0.6 apply the max option too late, causing excessive memory (~505 MB) and CPU (~800 ms) usage when expanding large numeric ranges. Fixed in version 5.0.6.