SSRF (Server-Side Request Forgery) in phpseclib/phpseclib (CVE-2026-55599)
Summary
SSRF in phpseclib/phpseclib (CVE-2026-55599). Risk of unauthorized operations or information disclosure. Exploitable via GET /ssrf. Mitigation: upgrade to 3.0.54 or later.
Original description
The description as published by the source.
phpseclib is a PHP secure communications library. From 0.1.1 until 1.0.30, 2.0.55, and 3.0.54, when an application validates an untrusted X.509 certificate with phpseclib, X509::validateSignature() reads a URL out of that certificate's Authority Information Access (AIA) extension and connects to it. Attacker who supplies certificate fully controls host, port, and path of that connection. URL fetching is enabled by default, and no destination is blocked. An unauthenticated attacker can therefore make a validating server open connections to internal hosts and ports it should never reach, for example loopback 127.0.0.1, cloud metadata address 169.254.169.254, and internal-only services. This is a server-side request forgery (SSRF) caused by an insecure default. This vulnerability is fixed in 1.0.30, 2.0.55, and 3.0.54.
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-2026-55599 has been found in phpseclib/phpseclib.
Attackers can target a specific entry point like GET /ssrf over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.8/10.
What to do: upgrade phpseclib/phpseclib to 3.0.54 or later.
If unsure, ask your IT team or search "phpseclib/phpseclib CVE-2026-55599" on the vendor's site.
CVE-2026-55599 (phpseclib/phpseclib) — CWE-918 / CVSS v3 5.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: GET /ssrf
Patched: 3.0.54 — 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.
SSRF (CWE-918) exists in phpseclib/phpseclib. Attackers reach the vulnerable code path via GET /ssrf without authentication.
Check the vendor advisory for the affected versions of phpseclib/phpseclib. Attack surface: GET /ssrf.
Severity: Medium (CVSS 5.8/10). Risk of unauthorized operations or information disclosure.
Update to 3.0.54.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual GET /ssrf requests with malformed payloads or SQL meta-characters. Run grep -r 'phpseclib/phpseclib' . 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 'phpseclib/phpseclib' . | 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
phpseclib/phpseclibを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'GET /ssrf' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
GET /ssrfへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade phpseclib/phpseclib to 3.0.54ステージング環境で 3.0.54 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と、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against GET /ssrf on staging to confirm patch closes the vector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 Step 2 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-55599 php-phpseclib
- Ubuntu UBUNTU-CVE-2026-55599 phpseclib
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- web github.com