NVD / CVE Program· CNA GitHub_M

CVE-2026-49283: SimpleSAMLphp HTTP-Artifact TLS validator confusion allows cross-IdP authentication bypass

Noroxi assessment

Priority: Monitor (action score 34/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.47% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. Administrator privileges are required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: simplesamlphp/saml2 (Packagist) 4.20.2, 5.0.6, 6.2.1; simplesamlphp/saml2-legacy (Packagist) 4.20.2, 4.19.3.

Low priority for now. Upgrade to simplesamlphp/saml2 (Packagist) 4.20.2, 5.0.6, 6.2.1; simplesamlphp/saml2-legacy (Packagist) 4.20.2, 4.19.3 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 8.7 · v3.1—No exploit Fix available

Published: Aug 19, 2026
Updated: Sep 18, 2026
EPSS: 0.4% · 40th percentile
CWE: CWE-295

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 34 / 40 · 8.7 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · GitHub_M: 8.7; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

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—

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This vulnerability is about certificate validation or weak cryptography. The free SSL checker tests your certificate, enabled TLS versions and weak ciphers.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

simplesamlphp saml2
- < 4.19.3, >= 4.20.0, < 4.20.2, >= 5.0.0, < 5.0.6, >= 6.0.0, < 6.2.1affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	simplesamlphp	from 0	—
Packagist	simplesamlphp/saml2	from 4.20.0 · before 4.20.2	4.20.2
Packagist	simplesamlphp/saml2	from 5.0.0 · before 5.0.6	5.0.6
Packagist	simplesamlphp/saml2	from 6.0.0 · before 6.2.1	6.2.1
Packagist	simplesamlphp/saml2	before 4.19.3	4.19.3
Packagist	simplesamlphp/saml2-legacy	from 4.20.0 · before 4.20.2	4.20.2
Packagist	simplesamlphp/saml2-legacy	before 4.19.3	4.19.3

Same product

simplesamlphp: all records

Other highest-scoring records for the same primary product.

CVE-2025-27773SimpleSAMLphp SAML2 library has incorrect signature verification for HTTP-Redirect binding
34Monitor
CVE-2024-52806SimpleSAMLphp SAML2 has an XXE in parsing SAML messages
33Monitor
CVE-2018-6519The SAML2 library before 1.10.4, 2.x before 2.3.5, and 3.x before 3.1.1 in SimpleSAMLphp has a Regular Expression Denial of Service vulnerab
31Monitor

Published before and after this one in the same product

← EarlierCVE-2023-49087Nov 30, 2023 · Validation of SignedInfo
30Monitor
Later →CVE-2026-49289Aug 19, 2026 · SimpleSAMLphp SAML2: Possible DoS via XPath Transform
30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Packagist:simplesamlphp/saml2	4.19.3	Package registry (OSV)
Packagist:simplesamlphp/saml2	4.20.2	Package registry (OSV)
Packagist:simplesamlphp/saml2	5.0.6	Package registry (OSV)
Packagist:simplesamlphp/saml2	6.2.1	Package registry (OSV)
Packagist:simplesamlphp/saml2-legacy	4.19.3	Package registry (OSV)
Packagist:simplesamlphp/saml2-legacy	4.20.2	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
Administrator privileges are required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector: Network
Attack complexity: Low
Privileges required: High
User interaction: None
Scope: Changed
Confidentiality impact: High
Integrity impact: High
Availability impact: None

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N

nvd-secondary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin

1override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {
2  // Left empty for the test environment
3}

Fixed

kotlin

1val client = OkHttpClient.Builder()
2  .certificatePinner(
3    CertificatePinner.Builder()
4      .add("api.sirius.example", "sha256/…")
5      .build()
6  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

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Change log

Fix✗ → ✓Sep 28, 2026, 10:45 PM UTC

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References

github.com/simplesamlphp/saml2/commit/4a71b20d8d845579fd0a54d6449c265b40db459d

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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