High severity · published Sep 2, 2026
CVE-2026-84382
HTTPX2: Streaming response decompression does not bound peak memory (decompression amplification)
7.5
CVSS
0.6%
EPSS
No
On KEV
Description
HTTPX2 is a next generation HTTP client for Python. Prior to 2.12.0, the HTTPX2 content decoders in src/httpx2/httpx2/_decoders.py fully inflate each gzip, deflate, br, or zstd network chunk before iter_bytes() or aiter_bytes() yields bounded pieces to the application. A 64 KiB compressed chunk can expand to approximately 64 MiB in one intermediate allocation, so an attacker-controlled or compromised server can cause severe memory pressure or out-of-memory process termination even when the application streams the response. This issue is fixed in version 2.12.0.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 50% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HT
httpx2 · pydantic
< 2.12.0 · source: vendor
Affected product
HT
httpx2
pydantic
More from httpx2
8.1
CVE-2026-84381
HTTPX2: Secure WebSocket traffic sent without TLS through SOCKS proxies
5.9
CVE-2026-84378
HTTPX2: Quadratic SSE line buffering can cause CPU denial of service
5.6
CVE-2026-84380
HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated
5.3
CVE-2026-84379
HTTPX2: Multipart part header injection via unvalidated file Content-Type and custom headers