brace-expansion DoS via unbounded expansion length causing an out-of-memory process crash

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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 with both count and string length until the process hits a fatal, uncatchable out-of-memory error. About 7.5 KB of input ('{a,b}'.repeat(1500)) crashes a default Node.js process. Any application that passes attacker-influenced strings to brace-expansion.expand() - directly or transitively via minimatch / glob brace patterns - can be crashed by a small request. Fixed in 5.0.8 by adding a maxLength option (default 4,000,000) that bounds accumulated output and intermediate arrays.

Source published

23 Jul 2026 12:54:23 UTC

Source modified

23 Jul 2026 14:44:41 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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 with both count and string length until the process hits a fatal, uncatchable out-of-memory error. About 7.5 KB of input ('{a,b}'.repeat(1500)) crashes a default Node.js process. Any application that passes attacker-influenced strings to brace-expansion.expand() - directly or transitively via minimatch / glob brace patterns - can be crashed by a small request. Fixed in 5.0.8 by adding a maxLength option (default 4,000,000) that bounds accumulated output and intermediate arrays.

Source published

23 Jul 2026 14:17:00 UTC

Source modified

24 Oct 2026 13:10:00 UTC

Observed here

25 Oct 2026 05:17:25 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 22e2d327-25fe-45d7-9f0c-dcd23b7108df · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

### Summary `expand()` bounds the *number* of results it produces (the `max` option, `100_000` by default) but not their *length*. By chaining many brace groups, an attacker keeps the result count under `max` while making every result grow with the number of groups. Building `max` long results — plus the intermediate arrays combined at each brace group — exhausts memory and crashes the Node process with an **uncatchable** out-of-memory error. `try/catch` around `expand()` does not help: the fatal error terminates the process. A ~7.5 KB input (`'{a,b}'.repeat(1500)`) is enough to crash a default Node process. ### Details For `N` chained brace groups such as `'{a,b}'.repeat(N)`: - the result count is `2^N`, immediately capped at `max` (`100_000`), so the `max` protection appears to hold, but - each result is `N` characters long, so the total output size is `max × N` characters, which grows without bound in `N`. `expand_` combines each brace set with the fully-expanded tail: ```js const post = m.post.length ? expand_(m.post, max, false) : [''] ... for (let j = 0; j < N.length; j++) { for (let k = 0; k < post.length && expansions.length < max; k++) { const expansion = pre + N[j] + post[k] // grows one group longer per level ... expansions.push(expansion) } } ``` The loop guard `expansions.length < max` limits how many strings are built, but nothing limits how long they get. Each recursion level materializes another array of up to `max` strings, one character longer than the level below, and — because V8 represents `pre + N[j] + post[k]` as a cons-string (rope) that references `post[k]` — those intermediate strings stay reachable through the whole chain. Memory therefore scales with `max × N`. Measured on `5.0.7` (`'{a,b}'.repeat(N)`, default `max`): | groups (N) | input bytes | result count | peak RSS | |---|---|---|---| | 20 | 100 | 100,000 | ~80 MB | | 50 | 250 | 100,000 | ~214 MB | | 100 | 500 | 100,000 | ~409 MB | | 300 | 1,500 | 100,000 | ~1,148 MB | | 1500 | 7,500 | — | **OOM crash** | ### Proof of concept ```js const { expand } = require('brace-expansion') // ~7.5 KB input — crashes the process with a fatal, uncatchable OOM: // FATAL ERROR: ... JavaScript heap out of memory try { expand('{a,b}'.repeat(1500)) } catch (e) { // never reached — the process is already dead } ``` ### Impact Any application that passes attacker-influenced strings to `brace-expansion.expand()` — directly, or transitively via `minimatch` / `glob` brace patterns — can be crashed by a small request. Because the failure is a fatal V8 out-of-memory error rather than a thrown exception, it cannot be caught and it takes down the whole worker/process, denying service. ### Remediation Upgrade to a patched release. The fix bounds the total number of characters a single `expand()` call may accumulate (`EXPANSION_MAX_LENGTH`, default `4_000_000`, configurable via a new `maxLength` option), applied inside the output-building loops so intermediate arrays are bounded too. Once the limit is reached, output is truncated — consistent with how `max` already truncates — instead of growing without bound. The limit sits well above any realistic expansion (100,000 results hitting `max` measure ~1M characters), so legitimate input is unaffected. After the fix, `'{a,b}'.repeat(1500)` returns a bounded, truncated result in ~0.7 s using ~340 MB and never crashes, including under a constrained 512 MB heap. The fix bounds memory but the algorithm still rebuilds intermediate arrays at each level (roughly `O(N × maxLength)` work on this input class). A streaming rewrite that produces output in `O(total output size)` can be a non-urgent follow-up. If immediate upgrade isn't possible, avoid passing untrusted input to `expand()` / glob brace patterns, or pass a small explicit `max` **and** `maxLength`.

Source published

24 Jul 2026 21:53:14 UTC

Source modified

10 Sep 2026 03:50:12 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH