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CVE-2026-14257 high CVSS 7.5

Vulnerability in brace-expansion (CVE-2026-14257)

Summary

Vulnerability in brace-expansion (CVE-2026-14257). Risk of unauthorized operations or information disclosure. Exploitable via max. Mitigation: upgrade to 1.1.17 or later.

Original description

The description as published by the source.

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:

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 c…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-14257 has been found in brace-expansion.
Attackers can target a specific entry point like max over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade brace-expansion to 1.1.17 or later.
If unsure, ask your IT team or search "brace-expansion CVE-2026-14257" on the vendor's site.

CVE-2026-14257 (brace-expansion) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: max / expand_ / minimatch / glob
Patched: 1.1.17 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-400) exists in brace-expansion. Attackers reach the vulnerable code path via max without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of brace-expansion. Attack surface: max / expand_ / minimatch / glob.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.1.17.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'brace-expansion' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'brace-expansion' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で brace-expansion を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade brace-expansion to 1.1.17

    ステージング環境で 1.1.17 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm brace-expansion
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.17"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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