# CVE-2026-118515: Symfony Serializer arbitrary file handling via DataUriNormalizer

Source: https://junglewise.ai/threats/cve-2026-118515-the-symfony-serializer-component-dataurinormalizer-handles-only  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-06. Updated: 2026-11-06  
License: CC BY 4.0 with a link back

CVE-2026-118515 · Severity: info · Published 2026-11-06

Symfony's Serializer component can be tricked into treating arbitrary files on a server as uploaded files when deserializing untrusted data. An attacker can craft a malicious request to access, expose, or move any file readable by the PHP process without sending it as a genuine upload, potentially exposing sensitive configuration files like .env.local or facilitating file manipulation attacks.

Vendors: [Symfony](https://junglewise.ai/threats/vendors/symfony).

## Quick answers

**Is CVE-2026-118515 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-118515 being exploited in the wild.

**How severe is CVE-2026-118515?** Informational severity, published 6 November 2026.

**Which products and versions are affected?** Symfony Serializer component prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, 8.x prior to 8.1.11.

**Is there a fix for CVE-2026-118515?** Yes: fixed in Symfony 5.4.56, 6.4.50, 7.4.23, 8.1.11. Until then: Ensure DataUriNormalizer is configured ahead of ObjectNormalizer in the serializer; the default FrameworkBundle configuration is protected by this fix. Avoid deserializing untrusted data into types with UploadedFile properties, particularly when using #[MapRequestPayload] on DTOs without authentication checks. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-118515 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-118515?** Check whether you run Symfony Serializer component at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Symfony 5.4.56, 6.4.50, 7.4.23, 8.1.11

Ensure DataUriNormalizer is configured ahead of ObjectNormalizer in the serializer; the default FrameworkBundle configuration is protected by this fix. Avoid deserializing untrusted data into types with UploadedFile properties, particularly when using #[MapRequestPayload] on DTOs without authentication checks.

## Technical details

The DataUriNormalizer only recognizes exact types SplFileInfo, SplFileObject, and File, so subclasses like UploadedFile bypass the normalizer and are instantiated through ObjectNormalizer with attacker-controlled constructor arguments including arbitrary file paths. By setting test: true in the request payload, UploadedFile::isValid() skips the is_uploaded_file() check, and move() falls back to rename(), allowing arbitrary file operations. File validation assertions do not prevent this since they validate against the attacker-chosen path on the server.

## Affected products

- Symfony Serializer component prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, 8.x prior to 8.1.11

## Timeline

- 2026-11-06: disclosed

## Related threats

- [Symfony Serializer ObjectNormalizer property traversal bypass](https://junglewise.ai/threats/cve-2026-122053-the-symfony-serializer-component-objectnormalizer-treats-any)