Cross-Site Scripting (XSS) in github.com/vapor/leaf-kit (CVE-2021-37634)
Summary
Cross-site scripting in github.com/vapor/leaf-kit (CVE-2021-37634). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 1.3.0 or later.
Original description
The description as published by the source.
Leafkit is a templating language with Swift-inspired syntax. Versions prior to 1.3.0 are susceptible to Cross-site Scripting (XSS) attacks. This affects anyone passing unsanitised data to Leaf's variable tags. Before this fix, Leaf would not escape any strings passed to tags as variables. If an attacker managed to find a variable that was rendered with their unsanitised data, they could inject scripts into a generated Leaf page, which could enable XSS attacks if other mitigations such as a Content Security Policy were not enabled. This has been patched in 1.3.0. As a workaround sanitize any untrusted input before passing it to Leaf and enable a CSP to block inline script and CSS data.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
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-2021-37634 has been found in github.com/vapor/leaf-kit.
Risk of unauthorized operations or information disclosure.
What to do: upgrade github.com/vapor/leaf-kit to 1.3.0 or later.
If unsure, ask your IT team or search "github.com/vapor/leaf-kit CVE-2021-37634" on the vendor's site.
CVE-2021-37634 (github.com/vapor/leaf-kit) — CWE-79
Attack vector: remote (network-reachable) / unauthenticated
Patched: 1.3.0 — 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.
Cross-site scripting (XSS) (CWE-79) exists in github.com/vapor/leaf-kit.
Check the vendor advisory for the affected versions of github.com/vapor/leaf-kit.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 1.3.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/vapor/leaf-kit' . 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
-
1Identify exposure identify
grep -r 'github.com/vapor/leaf-kit' . | 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
github.com/vapor/leaf-kitを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade github.com/vapor/leaf-kit to 1.3.0ステージング環境で 1.3.0 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。
-
3Post-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
References
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web github.com