Vulnerability in github.com/xyproto/algernon (CVE-2026-46430)
Summary
Vulnerability in github.com/xyproto/algernon (CVE-2026-46430). Risk of unauthorized operations or information disclosure. Exploitable via http.Server.Addr. Mitigation: upgrade to 1.17.7 or later.
Original description
The description as published by the source.
Summary
The SSE event server bound to 0.0.0.0:5553 on Linux/macOS by default because the platform-dependent host default in engine/flags.go:39-46 set host = "" for non-Windows, and utils.JoinHostPort("", ":5553") resolves to ":5553" — a Go http.Server.Addr of ":5553" listens on every interface. On Windows the same code chose "localhost", binding loopback only.
The result was a platform split where the OS Algernon's dev workflow is most often used on (Linux/macOS) got the network-exposed default, and only Windows users got the loopback-safe one. A LAN peer with no developer interaction could connect to :5553 and read the file-change stream.
This advisory covers the bind-address default in isolation. The fix is independent of authentication (#2a) and CORS (#2b) — switching the default to loopback can be done without touching either.
Details
Root cause — platform-dependent host default in handleFlags
// engine/flags.go:39-46 (1.17.6)
host := ""
if runtime.GOOS == "windows" {
host = "localhost"
// Default Bolt database file
ac.defaultBoltFilename = filepath.Join(serverTempDir, "algernon.db")
// Default log file
ac.defaultLogFile = filepath.Join(serverTempDir, "algernon.log")
}
// engine/config.go:388-391 (1.17.6, finalConfiguration)
if ac.eventAddr == "" {
ac.eventAddr = utils.JoinHostPort(host, ac.defaultEventColonPort)
}
Result tabulated:
| Platform | host | eventAddr after `JoinHostPo…
Source: GitHub Security Advisories (Global) 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-2026-46430 has been found in github.com/xyproto/algernon.
Attackers can target a specific entry point like http.Server.Addr over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 4.3/10.
What to do: upgrade github.com/xyproto/algernon to 1.17.7 or later.
If unsure, ask your IT team or search "github.com/xyproto/algernon CVE-2026-46430" on the vendor's site.
CVE-2026-46430 (github.com/xyproto/algernon) — CWE-1188 / CVSS v3 4.3
Attack vector: adjacent-network / unauthenticated / no user interaction
Attack surface: http.Server.Addr / host / handleFlags / eventAddr
Patched: 1.17.7 — 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.
A vulnerability (CWE-1188) exists in github.com/xyproto/algernon. Attackers reach the vulnerable code path via http.Server.Addr without authentication.
Check the vendor advisory for the affected versions of github.com/xyproto/algernon. Attack surface: http.Server.Addr / host / handleFlags / eventAddr.
Severity: Medium (CVSS 4.3/10). Risk of unauthorized operations or information disclosure.
Update to 1.17.7.
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/xyproto/algernon' . 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/xyproto/algernon' . | 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/xyproto/algernon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/xyproto/algernon to 1.17.7ステージング環境で 1.17.7 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
- package github.com
- web github.com
- web github.com