vulnerability / NVI-00012968 / Revision 1
tornado: CurlAsyncHTTPClient enforces no response-size limit — decompression bomb drives unbounded memory accumulation to OOM
GitHub lists this reviewed advisory for tornado. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
7.5 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
tornado
source listed<= 6.5.8
An unbounded memory accumulation (decompression bomb) in `tornado.curl_httpclient.CurlAsyncHTTPClient` — the client-side sibling gap of CVE-2026-49855 — verified end-to-end on the 2026-08-15 master snapshot (`6.6.dev1`) and present unchanged in the latest release tag `v6.5.8` and on master (checked 2026-08-17). When a Tornado application configures the curl client (the documented deployment for proxy support / advanced TLS options) and `fetch()`es an attacker-chosen or attacker-compromised URL with default `decompress_response=True`, a malicious server replying `Content-Encoding: gzip` with a ~2.8 MB wire bomb drove the client's RSS from 30,884 kB to **1,032,100 kB (~1008 MB) in 3.18 s** (~350 MB/s, monotonic, no plateau) until the kernel OOM-killed the process (exit 137, cgroup `OOMKilled=true`) — with the transfer only 67% complete and **no client-side size check ever intervening**: `curl_httpclient.py` contains zero occurrences of `max_body_size`/`MAXFILESIZE`. The identical bomb against the default `SimpleAsyncHTTPClient` fails cleanly at ~65 MB, because every size gate CVE-2026-49855 added (compressed CL, chunked total, cumulative decompressed size — `http1connection.py:620,67
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-chx6-46f5-w4vp ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.