ghsa-5vjj-2r48-q622
CVSS 6.9 github### Impact **Who is impacted**: - Any application using Zapros to make HTTP requests to untrusted servers - Applications that follow redirects to attacker-controlled hosts **Attack vector**: - A malicious HTTP server returns a response with many chained content encodings. When the client attempts to decode, it creates a deeply nested decompression chain consuming excessive resources. ### Patches Fixed in version 0.14.0. The fix adds a hardcoded limit of **5** `Content-Encoding` layers. Responses exceeding this limit raise `DecodingError`. ### Workarounds Add middleware that checks for a malicious Content-Encoding header. ```python from typing import cast from zapros import ( AsyncBaseHandler, AsyncBaseMiddleware, BaseHandler, BaseMiddleware, Client, DecodingError, Request, Response, ) MAX_DECODE_LAYERS = 5 class ContentEncodingCheckMiddleware(BaseMiddleware, AsyncBaseMiddleware): def __init__( self, next_handler: BaseHandler | AsyncBaseHandler, *, max_layers: int = MAX_DECODE_LAYERS, ) -> None: self.next = cast(BaseHandler, next_handler) self.async_next = cast(AsyncBaseHandler, next_handler) self._max_layers = max_layers def _check(self, response: Response) -> None: encoding_header = response.headers.get("Content-Encoding") if not encoding_header: return layers = [enc.strip().lower() for enc in encoding_header.split(",") if enc.strip()] if len(layers) > self._max_layers: raise DecodingError(f"Too many Content-Encoding layers ({len(layers)}), maximum is {self._max_layers}") def handle(self, request: Request) -> Response: response = self.next.handle(request) self._check(response) return response async def ahandle(self, request: Request) -> Response: response = await self.async_next.ahandle(request) self._check(response) return response with Client().wrap_with_middleware(lambda next: ContentEncodingCheckMiddleware(next)) as client: ... ```
- Published
- unknown
- Last Modified
- unknown
CVSS details not available.
No product information available.
No linked vulnerabilities found.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "zapros"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.14.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-61541"
],
"database_specific": {
"cwe_ids": [
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-09-23T13:58:35Z",
"nvd_published_at": "2026-09-21T22:16:57Z",
"severity": "MODERATE"
},
"details": "### Impact\n\n**Who is impacted**:\n - Any application using Zapros to make HTTP requests to untrusted servers\n - Applications that follow redirects to attacker-controlled hosts\n\n**Attack vector**:\n - A malicious HTTP server returns a response with many chained content encodings. When the client attempts to decode, it creates a deeply nested decompression chain consuming excessive resources.\n\n### Patches\n\nFixed in version 0.14.0.\n\n The fix adds a hardcoded limit of **5** `Content-Encoding` layers. Responses exceeding this limit raise `DecodingError`.\n\n### Workarounds\n\nAdd middleware that checks for a malicious Content-Encoding header.\n\n```python\nfrom typing import cast\n\nfrom zapros import (\n AsyncBaseHandler,\n AsyncBaseMiddleware,\n BaseHandler,\n BaseMiddleware,\n Client,\n DecodingError,\n Request,\n Response,\n)\n\nMAX_DECODE_LAYERS = 5\n\n\nclass ContentEncodingCheckMiddleware(BaseMiddleware, AsyncBaseMiddleware):\n def __init__(\n self,\n next_handler: BaseHandler | AsyncBaseHandler,\n *,\n max_layers: int = MAX_DECODE_LAYERS,\n ) -> None:\n self.next = cast(BaseHandler, next_handler)\n self.async_next = cast(AsyncBaseHandler, next_handler)\n self._max_layers = max_layers\n\n def _check(self, response: Response) -> None:\n encoding_header = response.headers.get(\"Content-Encoding\")\n if not encoding_header:\n return\n\n layers = [enc.strip().lower() for enc in encoding_header.split(\",\") if enc.strip()]\n if len(layers) > self._max_layers:\n raise DecodingError(f\"Too many Content-Encoding layers ({len(layers)}), maximum is {self._max_layers}\")\n\n def handle(self, request: Request) -> Response:\n response = self.next.handle(request)\n self._check(response)\n return response\n\n async def ahandle(self, request: Request) -> Response:\n response = await self.async_next.ahandle(request)\n self._check(response)\n return response\n\n\nwith Client().wrap_with_middleware(lambda next: ContentEncodingCheckMiddleware(next)) as client:\n ...\n```",
"id": "GHSA-5vjj-2r48-q622",
"modified": "2026-09-23T13:58:35Z",
"published": "2026-09-23T13:58:35Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/kap-sh/zapros/security/advisories/GHSA-5vjj-2r48-q622"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61541"
},
{
"type": "WEB",
"url": "https://github.com/kap-sh/zapros/commit/7971fbca9707eb01455ca2d73416ac091f96908b"
},
{
"type": "PACKAGE",
"url": "https://github.com/kap-sh/zapros"
},
{
"type": "WEB",
"url": "https://github.com/kap-sh/zapros/releases/tag/v0.14.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Zapros has an Unbounded Content-Encoding decompression chain that allows denial of service"
}