Denial of service via memory exhaustion. Affects all callers who streamed compressed responses relying on the chunk size — explicit (iterbytes(chunksize=...)) 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// patchesUpgrade to 0.14.0 or later. The decoders now bound the output of each decompression step to the requested chunksize: gzip/deflate via zlib's maxlength + unconsumedtail, brotli via outputbufferlimit, and zstd via a bounded streamwriter. Peak memory during streaming decode is now proportional to chunksize for all supported encodings.
// workaroundsFor unpatched versions:
- Read the still-compressed body with Response.iterraw() / Response.asynciterraw(), which bypass the built-in decoders, and decompress it yourself with an explicit output-size bound (e.g. zlib's maxlength), 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.
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
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- High
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None