Vulnerability in simplesamlphp/saml2 (CVE-2026-49283)
Summary
Vulnerability in simplesamlphp/saml2 (CVE-2026-49283). Confidential information can be exposed externally. Exploitable via Response. Mitigation: upgrade to 4.19.3 or later.
Original description
The description as published by the source.
The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. Prior to versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1, the HTTPArtifact::receive() flow can treat an unsigned embedded SAML Response as cryptographically valid for the wrong identity provider. SOAPClient::addSSLValidator() attaches a TLS-based validator to the outer SOAP ArtifactResponse, while the embedded Response receives a validator that delegates to the outer message and is later checked against metadata selected from the embedded response issuer rather than necessarily the artifact issuer. SOAPClient::validateSSL() returns normally when the TLS public key does not match the key being validated, and SAML2\Message::validate() treats a validator call that does not throw as successful. In a multi-IdP federation, a malicious or lower-trust IdP can therefore provide an ArtifactResponse containing an unsigned Response that claims a higher-trust victim IdP as issuer and authenticate as arbitrary users with attacker-chosen assertion attributes, NameID, and session data. This issue is fixed in versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1.
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-2026-49283 has been found in simplesamlphp/saml2.
Attackers can target a specific entry point like Response over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.7/10.
What to do: upgrade simplesamlphp/saml2 to 4.19.3 or later.
If unsure, ask your IT team or search "simplesamlphp/saml2 CVE-2026-49283" on the vendor's site.
CVE-2026-49283 (simplesamlphp/saml2) — CWE-295 / CVSS v3 8.7
Attack vector: remote (network-reachable) / no user interaction
Attack surface: Response / ArtifactResponse / NameID
Patched: 4.19.3 — 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-295) exists in simplesamlphp/saml2. Attackers reach the vulnerable code path via Response.
Check the vendor advisory for the affected versions of simplesamlphp/saml2. Attack surface: Response / ArtifactResponse / NameID.
Severity: High (CVSS 8.7/10). Confidential information can be exposed externally.
Update to 4.19.3.
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 'simplesamlphp/saml2' . 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
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1Identify exposure identify
grep -r 'simplesamlphp/saml2' . | 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
simplesamlphp/saml2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 simplesamlphp/saml2 to 4.19.3ステージング環境で 4.19.3 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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-49283 simplesamlphp
- Ubuntu UBUNTU-CVE-2026-49283 simplesamlphp
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- patch github.com
- patch github.com
- patch github.com
- web github.com