# CVE-2026-49289: SimpleSAMLphp SAML2: Possible DoS via XPath Transform

> Remote unauthenticated attackers can cause denial of service in SimpleSAMLphp SAML2 library by sending crafted SAML messages with XPath transforms.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-49289, GHSA-5cjr-mxj5-wmrx, UBUNTU-CVE-2026-49289

## What is CVE-2026-49289?

CVE-2026-49289 is a high-severity denial of service vulnerability in simplesamlphp saml2, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. In 4.19.2 and 4.20.2, the library permits attacker-controlled XPath transforms while processing XML signatures in specially crafted SAML messages. XPath evaluation can consume uncontrolled processing resources, allowing a remote unauthenticated attacker to deny service to any entity relying on SimpleSAMLphp or directly on the SAML2 library. The mitigation limits the number of transforms, permits only transform algorithms identified by the SAML 2.0 Core specification, and specifically rejects XPath transforms. This issue is fixed in versions 4.19.3 and 4.20.3.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-49289?

8 open source packages ship an affected version, including simplesamlphp/saml2 and simplesamlphp/saml2-legacy.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `simplesamlphp/saml2` | Packagist | All versions | 4.19.3 |
| `simplesamlphp/saml2` | Packagist | All versions | 4.19.3 |
| `simplesamlphp/saml2` | Packagist | From 4.20.0 | 4.20.3 |
| `simplesamlphp/saml2` | Packagist | From 4.20.0 | 4.20.3 |
| `simplesamlphp/saml2-legacy` | Packagist | All versions | 4.19.3 |
| `simplesamlphp/saml2-legacy` | Packagist | All versions | 4.19.3 |
| `simplesamlphp/saml2-legacy` | Packagist | From 4.20.0 | 4.20.3 |
| `simplesamlphp/saml2-legacy` | Packagist | From 4.20.0 | 4.20.3 |

## How do I fix CVE-2026-49289?

Upgrade simplesamlphp/saml2 to a fixed version for your release line: 4.19.3 or 4.20.3.

## Is CVE-2026-49289 being exploited?

There is no known exploitation of CVE-2026-49289 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-49289 and fix it if it is affected.

What it is: CVE-2026-49289 is a high-severity denial of service vulnerability in simplesamlphp saml2, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-49289 in the wild and no public exploit code.

Affected packages and fixed versions:
- simplesamlphp/saml2 (Packagist): affected all versions; fixed in 4.19.3
- simplesamlphp/saml2 (Packagist): affected all versions; fixed in 4.19.3
- simplesamlphp/saml2 (Packagist): affected from 4.20.0; fixed in 4.20.3
- simplesamlphp/saml2 (Packagist): affected from 4.20.0; fixed in 4.20.3
- simplesamlphp/saml2-legacy (Packagist): affected all versions; fixed in 4.19.3
- simplesamlphp/saml2-legacy (Packagist): affected all versions; fixed in 4.19.3
- simplesamlphp/saml2-legacy (Packagist): affected from 4.20.0; fixed in 4.20.3
- simplesamlphp/saml2-legacy (Packagist): affected from 4.20.0; fixed in 4.20.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-49289/ (Markdown: https://insights.sbomify.com/CVE-2026-49289/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-49289
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-49289
- OSV: https://osv.dev/vulnerability/CVE-2026-49289

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-49289/
Summaries are generated and may contain mistakes; the official description above is the record.