Quick answers
- Is CVE-2026-123817 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-123817 being exploited in the wild.
- How severe is CVE-2026-123817?
- Informational severity, published 9 November 2026.
- Which products and versions are affected?
- Aio-Libs Aiohttp prior to 3.14.4.
- Is there a fix for CVE-2026-123817?
- Yes: fixed in 3.14.4. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-123817 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-123817?
- Check whether you run Aio-Libs Aiohttp at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: 3.14.4
Technical details
The WebSocket reader retains one bytes object for each transport read while reassembling incomplete frames, allowing per-object overhead to substantially exceed payload bytes allowed by max_msg_size. A malicious peer splits a frame into many tiny reads to trigger excessive memory consumption. The fix caps the number of per-read payload fragments retained in memory to max(1024, max_msg_size // 256).
Affected products
- aio-libs AIOHTTP prior to 3.14.4
Timeline
- 2026-11-09: disclosed