# GHSA-rjpm-qmq7-q85w: Symfony XXE security vulnerability > An attacker can cause a Denial of Service by sending crafted XML with entity expansion, exhausting server memory. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 30 May 2024 ## What is GHSA-rjpm-qmq7-q85w? GHSA-rjpm-qmq7-q85w is a denial of service vulnerability in symfony/routing, published on 30 May 2024. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Symfony 2.0.11 carried a [similar] XXE security fix, however, on review of ZF2 I also noted a vulnerability to XML Entity Expansion (XEE) attacks whereby all extensions making use of libxml2 have no defense against XEE Quadratic Blowup Attacks. The vulnerability is a function of there being no current method of disabling custom entities in PHP (i.e. defined internal to the XML document without using external entities). In a QBA, a long entity can be defined and then referred to multiple times in document elements, creating a memory sink with which Denial Of Service attacks against a host's RAM can be mounted. The use of the LIBXML_NOENT or equivalent option in a dependent extension amplified the impact (it doesn't actually mean "No Entities"). In addition, libxml2's innate defense against the related Exponential or Billion Laugh's XEE attacks is active only so long as the LIBXML_PARSEHUGE is NOT set (it disables libxml2's hardcoded entity recursion limit). No instances of these two options were noted, but it's worth referencing for the future. Consider this (non-fatal) example: ``` ]> &a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a; ``` Increase the length of entity, and entity count to a few hundred, and peak memory usage will waste no time spiking the moment the nodeValue for is accessed since the entities will then be expanded by a simple multiplier effect. No external entities required. ... This can be used in combination with the usual XXE defense of calling libxml_disable_entity_loader(TRUE) and, optionally, the LIBXML_NONET option (should local filesystem access be allowable). The DOCTYPE may be removed instead of rejecting the XML outright but this would likely result in other problems with the unresolved entities. ## Which versions are affected by GHSA-rjpm-qmq7-q85w? 2 open source packages ship an affected version, including symfony/routing. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `symfony/routing` | Packagist | From 2.0.0 | 2.0.17 | | `symfony/routing` | Packagist | From 2.0.0 | 2.0.17 | ## How do I fix GHSA-rjpm-qmq7-q85w? Upgrade symfony/routing to 2.0.17 or later. ## Is GHSA-rjpm-qmq7-q85w being exploited? There is no known exploitation of GHSA-rjpm-qmq7-q85w in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for GHSA-rjpm-qmq7-q85w and fix it if it is affected. What it is: GHSA-rjpm-qmq7-q85w is a denial of service vulnerability in symfony/routing, published on 30 May 2024. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of GHSA-rjpm-qmq7-q85w in the wild and no public exploit code. Affected packages and fixed versions: - symfony/routing (Packagist): affected from 2.0.0; fixed in 2.0.17 - symfony/routing (Packagist): affected from 2.0.0; fixed in 2.0.17 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/GHSA-rjpm-qmq7-q85w/ (Markdown: https://insights.sbomify.com/GHSA-rjpm-qmq7-q85w/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/GHSA-rjpm-qmq7-q85w --- From sbomify Insights: https://insights.sbomify.com/GHSA-rjpm-qmq7-q85w/ Summaries are generated and may contain mistakes; the official description above is the record.