CVE-2026-121623 Affecting symfony package, versions <6.4.50+dfsg-0+deb13u1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published7 Nov 2026
- disclosed6 Nov 2026
Introduced: 6 Nov 2026
NewCVE-2026-121623 (opens in a new tab)How to fix?
Upgrade Echo:latest symfony to version 6.4.50+dfsg-0+deb13u1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream symfony package and not the symfony package as distributed by Echo.
See How to fix? for Echo:latest relevant fixed versions and status.
The Symfony Serializer component DataUriNormalizer::denormalize() matches the data: scheme with a case-sensitive regular expression, allowing a value with an uppercase scheme, such as DATA:,/../../../etc/passwd, to bypass it, resulting in Arbitrary Local File Read through Path Traversal 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 value whose scheme is not lowercase data: are treated as a local file path and opened instead of being decoded as inline data, so the resulting File, \SplFileInfo, or \SplFileObject points at a file on the server, which the application then handles as the uploaded content.
Any endpoint that deserializes untrusted input into one of these types is affected. FrameworkBundle registers DataUriNormalizer ahead of ObjectNormalizer by default. A single request with a crafted DATA: value is enough to read arbitrary local files that the application can access, with no authentication needed if the endpoint is public.