High, CVSS 7.5PackagistPublished
symfony/translation XML Entity Expansion vulnerability
GHSA-f75p-x5vm-83qp
- Affected
- Packagist symfony/translation >= 2.0.0, < 2.0.17
- Fixed in
- 2.0.17· Vendor fix available
- Issue
- 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 LIBXMLNOENT 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 LIBXMLPARSEHUGE is NOT set (it disables libxml2's hardcoded entity recursion limit). No instances of these two…
Recommended action: Upgrade to 2.0.17 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.