FileStore key canonicalization collisions allow response cache mixup/poisoning (ASCII ord + Unicode NFKD)

published 2026-02-09 8 mo ago modified 2026-07-13 3 mo ago also EUVD-2026-6498 , GHSA-vxqx-rh46-q2pg , PYSEC-2026-2197

cvss: 6.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits: 0; none known

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.

Patch / fix

fixed in 2 links 2

pypi litestar 2.20.0
litestar litestar 2.20.0

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 8 mo ago (2026-02-10)

Exploit prediction

0.46% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/litestar-org/litestar/security/advisories/GHSA-vxqx-rh46-q2pg referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
GitHub	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
OSV	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
pypi	litestar	>=2.19.0, <2.20.0 <2.20.0	2.20.0

Affected products

litestar-org litestar

Classification

Weakness

CWE-176 Improper Handling of Unicode Encoding
CWE-20 Improper Input Validation

References

github.com /litestar-org/litestar/commit/85db6183a76f8a6b3fd6ee3c88d860b9f37a2cca
web, patch
github.com /litestar-org/litestar/security/advisories/GHSA-vxqx-rh46-q2pg
web, exploit, vendor-advisory, evidence
docs.litestar.dev /2/release-notes/changelog.html#2.20.0
web, release-notes, advisory
github.com /litestar-org/litestar/releases/tag/v2.20.0
web, release-notes, advisory
nvd.nist.gov /vuln/detail/CVE-2026-25480
advisory
github.com /litestar-org/litestar
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary