GHSA-6CP7-3M3C-5X5C
Vulnerability from github – Published: 2026-09-23 13:57 – Updated: 2026-09-23 13:57Impact
Denial of service via memory exhaustion. Affects all callers who streamed compressed responses relying on the chunk size — explicit (iter_bytes(chunk_size=...)) or the default — to bound memory. The decoder ignored that bound, so a chunk could be far larger than requested and a single compressed response could overflow memory.
import gzip, zapros
# Server returns ~1 GiB of zeros gzip-compressed to ~1 MiB,
# with header: Content-Encoding: gzip
bomb = gzip.compress(b"\0" * 1_000_000_000) # ~1 MiB on the wire
with zapros.stream("GET", "https://malicious.example/bomb") as response:
# Caller asks for 8 KiB chunks, expecting bounded memory:
for chunk in response.iter_bytes(chunk_size=8192):
... # first `chunk` is ~1 GiB, not 8 KiB -> memory exhaustion
Patches
Upgrade to 0.14.0 or later. The decoders now bound the output of each decompression step to the requested chunk_size: gzip/deflate via zlib's max_length + unconsumed_tail, brotli via output_buffer_limit, and zstd via a bounded stream_writer. Peak memory during streaming decode is now proportional to chunk_size for all supported encodings.
Workarounds
For unpatched versions:
- Read the still-compressed body with Response.iter_raw() / Response.async_iter_raw(), which bypass the built-in decoders, and decompress it yourself with an explicit output-size bound (e.g. zlib's max_length), aborting once a configured limit is exceeded.
- Where feasible, send Accept-Encoding: identity to disable response compression so bodies are not decompressed client-side.
- Avoid decoding response bodies from untrusted servers.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "zapros"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.14.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-61652"
],
"database_specific": {
"cwe_ids": [
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-09-23T13:57:48Z",
"nvd_published_at": "2026-09-21T22:16:57Z",
"severity": "HIGH"
},
"details": "### Impact\n\nDenial of service via memory exhaustion. Affects all callers who streamed compressed responses relying on the chunk size \u2014 explicit (`iter_bytes(chunk_size=...)`) or the default \u2014 to bound memory. The decoder ignored that bound, so a chunk could be far larger than requested and a single compressed response could overflow memory.\n\n```python\nimport gzip, zapros\n\n# Server returns ~1 GiB of zeros gzip-compressed to ~1 MiB,\n# with header: Content-Encoding: gzip\nbomb = gzip.compress(b\"\\0\" * 1_000_000_000) # ~1 MiB on the wire\n\nwith zapros.stream(\"GET\", \"https://malicious.example/bomb\") as response:\n # Caller asks for 8 KiB chunks, expecting bounded memory:\n for chunk in response.iter_bytes(chunk_size=8192):\n ... # first `chunk` is ~1 GiB, not 8 KiB -\u003e memory exhaustion\n```\n\n### Patches\n\nUpgrade to `0.14.0` or later. The decoders now bound the output of each decompression step to the requested `chunk_size`: gzip/deflate via `zlib`\u0027s `max_length` + `unconsumed_tail`, brotli via `output_buffer_limit`, and zstd via a bounded `stream_writer`. Peak memory during streaming decode is now proportional to `chunk_size` for all supported encodings.\n\n### Workarounds\n\nFor unpatched versions:\n- Read the still-compressed body with `Response.iter_raw()` / `Response.async_iter_raw()`, which bypass the built-in decoders, and decompress it yourself with an explicit output-size bound (e.g. `zlib`\u0027s `max_length`), aborting once a configured limit is exceeded.\n- Where feasible, send `Accept-Encoding: identity` to disable response compression so bodies are not decompressed client-side.\n- Avoid decoding response bodies from untrusted servers.",
"id": "GHSA-6cp7-3m3c-5x5c",
"modified": "2026-09-23T13:57:48Z",
"published": "2026-09-23T13:57:48Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/kap-sh/zapros/security/advisories/GHSA-6cp7-3m3c-5x5c"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61652"
},
{
"type": "WEB",
"url": "https://github.com/kap-sh/zapros/commit/9b59fa65857734599c34b0b3dff4c2b62293a68d"
},
{
"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:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Zapros: Streaming decoders ignored the requested chunk size, allowing a single compressed response chunk to allocate unbounded memory (decompression bomb)"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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