CVE-2026-123824 Symfony: XXE (Local File Read) in Config XmlUtils::parse() via validateOnParse = true
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-123824?
CVE-2026-123824 is a low-severity vulnerability in sensiolabs symfony, published on 6 Nov 2026.
Official description
The Symfony Config component XmlUtils::parse() enables DTD validation before rejecting documents that carry a doctype, allowing XML external entity (XXE) injection in Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11. A remote attacker who can supply XML to this method can determine whether local files exist, cause a denial of service, and, in some configurations, exfiltrate local file content via a crafted XML document whose doctype declares an external file:// entity. XmlUtils::parse() sets $dom->validateOnParse = true before calling loadXML() and only rejects documents carrying a doctype afterwards. Enabling DTD validation makes libxml resolve external entities during loadXML(), and LIBXML_NONET blocks http:// but not file://, so a file:// entity is read from disk before the doctype rejection runs. The content of the file is not returned to the caller, but the distinct libxml error for a missing path reveals whether a file exists, and an entity pointing at a large or slow file causes a denial of service. If the application registers a network-capable stream wrapper such as s3://, a parameter entity can also send the content of a local file to an external server. This is the same issue as CVE-2026-45071, which was fixed in the DomCrawler component but not in Config.
Applications are affected if they pass untrusted XML to XmlUtils::parse() directly. The Symfony components that call it process developer-provided or operator-configured sources, such as configuration files and the XLIFF documents fetched by the translation providers.
Weakness: CWE-611
Which versions are affected by CVE-2026-123824?
How do I fix CVE-2026-123824?
Upgrade to a fixed version.
Is CVE-2026-123824 being exploited?
There is no known exploitation of CVE-2026-123824 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-123824, GHSA-5jff-8h8q-r5qx, UBUNTU-CVE-2026-123824.