6.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-25480

CVE-2026-25480: FileStore key canonicalization collisions allow response cache mixup/poisoning (ASCII ord + Unicode NFKD)

Litestar is an Asynchronous Server Gateway Interface (ASGI) framework. Prior to 2.20.0, FileStore maps cache keys to filenames using Unicode NFKD normalization and ord() substitution without separators, creating key collisions. When FileStore is used as response-cache backend, an unauthenticated remote attacker can trigger cache key collisions via crafted paths, causing one URL to serve cached responses of another (cache poisoning/mixup). This vulnerability is fixed in 2.20.0.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-25480

CVE-2026-25480:

6.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
litestar	pip	= 2.19.0	2.20.0

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability exists in the _safe_file_name function located in litestar/stores/file.py. This function's purpose is to convert cache keys into filesystem-safe filenames for the FileStore caching backend. The flaw in the original implementation was its use of a non-injective transformation—specifically, Unicode NFKD normalization combined with substituting non-alphanumeric characters with their ord() value. This created scenarios where different cache keys could be normalized to the identical filename, resulting in a key collision.

The patch, identified in commit 85db6183a76f8a6b3fd6ee3c88d860b9f37a2cca, rectifies this by replacing the weak normalization logic with the hashlib.blake2s cryptographic hash function. This ensures that distinct keys will produce unique filenames, thereby eliminating the collision vector.

During an exploit, an attacker would craft a request with a path that, when used as a cache key, collides with the key of another cached resource. This malicious key is processed by FileStore.set (to poison the cache) or FileStore.get (to retrieve a poisoned entry). Both methods rely on the vulnerable _safe_file_name function to resolve the key to a filename. Consequently, the functions that would be observed in a runtime profile during exploitation are _safe_file_name, FileStore.set, and FileStore.get.

Vulnerable functions

_safe_file_name

litestar/stores/file.py

The function `_safe_file_name` in `litestar/stores/file.py` is responsible for converting a cache key into a safe filename. The vulnerable version of this function used a combination of Unicode NFKD normalization and replacing non-alphanumeric characters with their ordinal values without a separator. This process is not injective, meaning multiple different keys can resolve to the same filename, causing a key collision. An attacker can craft specific cache keys (e.g., via request paths) to either overwrite or read cached content for a different key, leading to cache poisoning.

FileStore.set

litestar/stores/file.py

The `FileStore.set` method is used to store a value in the cache. It internally calls the vulnerable `_safe_file_name` function to determine the filename for the given key. When an attacker provides a crafted key, this method writes the cached data to a file whose name collides with that of another key, thus poisoning the cache.

FileStore.get

litestar/stores/file.py

The `FileStore.get` method is used to retrieve a value from the cache. It internally calls the vulnerable `_safe_file_name` function to determine the filename for the given key. An attacker can use this method with a crafted key to retrieve cached content that was stored for a different key, leading to information disclosure or serving of incorrect data.

Vulnerability Intelligence
Miggo AI

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WAF Rule

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Reasoning

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