# CVE-2026-54273: aio-libs aiohttp Denial of Service via unbounded request pipelining

Source: https://junglewise.ai/threats/cve-2026-54273-aio-libs-aiohttp-denial-of-service-via-unbounded-request  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-22. Updated: 2026-06-22  
License: CC BY 4.0 with a link back

CVE-2026-54273 · Severity: medium · CVSS 4 · Published 2026-06-22

AIOHTTP is a popular Python library used to build web servers and clients. A flaw in how it handles multiple simultaneous requests over a single connection allows an attacker to send a massive backlog of data that the server cannot process quickly enough. This can cause the server to consume all available memory, leading to a crash or service outage (Denial of Service).

Technologies: [aiohttp (PyPI)](https://junglewise.ai/threats/technologies/aiohttp). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-54273 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-54273 being exploited in the wild.

**How severe is CVE-2026-54273?** Medium severity, with a CVSS score of 4, published 22 June 2026.

**Which products and versions are affected?** aiohttp (PyPI) <= 3.14.0, ECOSYSTEM:introduced=0,fixed=3.14.1.

**Is there a fix for CVE-2026-54273?** Yes. aiohttp (PyPI): upgrade to 3.14.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-54273 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-54273?** Check whether you run aiohttp (PyPI) 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

- aiohttp (PyPI): upgrade to 3.14.1 or later

  ```sh
  pip install "aiohttp>=3.14.1"
  ```


## Technical details

A resource exhaustion vulnerability exists in AIOHTTP's HTTP/1.1 parser due to the lack of a limit on the number of parsed-but-unhandled pipelined requests buffered per connection. By sending a continuous stream of pipelined requests, a remote unauthenticated attacker can force the server to allocate an unbounded amount of memory to queue these requests while the handler is busy. This leads to a Denial of Service (DoS) condition via memory exhaustion. The fix, introduced in version 3.14.1, implements a bounded queue that pauses the transport once an internal limit is reached, resuming only as the request handler drains the backlog.

## Affected products

- aio-libs aiohttp < 3.14.1

## Identifiers

- CVE-2026-54273
- GHSA-4fvr-rgm6-gqmc
- PYSEC-2026-2107

## Timeline

- 2026-06-07: patched: Fix committed to repository
- 2026-06-08: advisory: GitHub Security Advisory published
- 2026-06-22: disclosed: NVD publication date

## References

- [https://github.com/aio-libs/aiohttp/commit/dfdfa9d5aad5d21f91c79fb2ceeba0f8046cb6cf](https://github.com/aio-libs/aiohttp/commit/dfdfa9d5aad5d21f91c79fb2ceeba0f8046cb6cf)
- [https://github.com/aio-libs/aiohttp/security/advisories/GHSA-4fvr-rgm6-gqmc](https://github.com/aio-libs/aiohttp/security/advisories/GHSA-4fvr-rgm6-gqmc)

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