CVE
aiohttp denial of service in pure-Python HTTP request parser
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
- Exploited
- No known exploitation
- Fix
- Fixed in 3.14.4
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Deployment uses the pure-Python HTTP parser (AIOHTTP_NO_EXTENSIONS set, or no standard C-extension wheel installed). The pipelined request queue is full, and a handler declines an upgrade request.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.42% · 37th percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 20/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
AIOHTTP, an asynchronous HTTP client and server framework for Python, is affected when its pure-Python request parser is in use, which can happen when the C extensions are disabled. A remote attacker who can send requests without logging in can make the parser buffer grow and replay already-handled requests, which can cause excessive memory use and repeated processing.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Original description
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, when the pipelined request queue is full, the pure-Python parser stores the unparsed remainder internally and also returns the same data to its caller. After a handler declines an upgrade request, the caller feeds the remainder back to the parser, causing the buffer to grow with each handled request and dispatching already-handled requests to the application again. The issue affects deployments using AIOHTTP_NO_EXTENSIONS or otherwise running without the standard C-extension wheel, and can cause excessive memory use and repeated request processing. This issue is fixed in version 3.14.4.
Who should check
Teams running aiohttp 3.14.3 or earlier with the pure-Python HTTP parser (AIOHTTP_NO_EXTENSIONS set or no standard wheel installed), especially servers handling pipelined requests.
“If users are using the Python parser ( AIOHTTP_NO_EXTENSIONS , or not a standard wheel installed)”
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure12/25Specific setups only, reachable over the network without a login
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.3/10CVSS 8.3
- No patch0/5No signal
What would change the score
- Would score about 70 if added to CISA KEV
- Would score about 65 if CISA's SSVC rates exploitation active
What to do
Check whether your setup matches what the bug needs.
Deployment uses the pure-Python HTTP parser (AIOHTTP_NO_EXTENSIONS set, or no standard C-extension wheel installed). The pipelined request queue is full, and a handler declines an upgrade request.Upgrade to a fixed version: 3.14.4.
Workaround: Switch to the default C parser.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-128130 (AIOHTTP: Pure-Python parser request replay and buffer growth behind a declined upgrade), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-128130 (entry last updated 2026-11-13):
Affected:
- aio-libs aiohttp: fixed in 3.14.4
Fixed versions: 3.14.4.
Vendor patches: 47babd8 (source: https://github.com/aio-libs/aiohttp/security/advisories/GHSA-28qf-cpwq-vmc2). Check each asset for these patch ids, not only its version.
Conditions (all must be true for the bug to be hit):
- Deployment uses the pure-Python HTTP parser (AIOHTTP_NO_EXTENSIONS set, or no standard C-extension wheel installed). (source: https://github.com/aio-libs/aiohttp/security/advisories/GHSA-28qf-cpwq-vmc2)
- The pipelined request queue is full, and a handler declines an upgrade request. (source: https://github.com/aio-libs/aiohttp/security/advisories/GHSA-28qf-cpwq-vmc2)
Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on.
Attacker needs: network access, no login, no user action.
Workaround: Switch to the default C parser. (source: https://github.com/aio-libs/aiohttp/security/advisories/GHSA-28qf-cpwq-vmc2)
CISA KEV: CVE-2026-128130 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-128130 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-28qf-cpwq-vmc2
- https://github.com/aio-libs/aiohttp/pull/13356
- https://github.com/aio-libs/aiohttp/pull/13360
- https://github.com/aio-libs/aiohttp/commit/47babd8c23ca79e2bae6cc8dcb5752b61e369fc7
- https://github.com/aio-libs/aiohttp/commit/72eaa429cf89b1e20212590f3e704444239569fb
- https://github.com/aio-libs/aiohttp/releases/tag/v3.14.4
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-128130
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-128130"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- aio-libs aiohttp
fixed in 3.14.4
Evidence 8
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 5
- Repository
- Repository
- Repository
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-128130
Is CVE-2026-128130 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
When the pipelined request queue is full, the pure-Python HTTP parser stores the unparsed remainder internally. A handler that declines an upgrade request can then cause that data to be replayed, so pipelined requests may be processed more than once and memory use can grow excessively.Source: github.com
Which versions are affected by CVE-2026-128130?
aiohttp: before 3.14.4.Source: cve.now feed data
Am I affected, and how do I check?
Deployments using the pure-Python HTTP parser are affected, which happens when AIOHTTP_NO_EXTENSIONS is set or when no standard C-extension wheel is installed. The affected range ends before aiohttp 3.14.4, so check the installed version with pip show aiohttp and whether AIOHTTP_NO_EXTENSIONS is set in the environment.Source: github.com
How do I fix CVE-2026-128130?
Upgrade aiohttp to 3.14.4 or later, which contains the fix in patch 47babd8.Source: github.com