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chore(deps): update dependency aiohttp to v3.13.4 [security]#234

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chore(deps): update dependency aiohttp to v3.13.4 [security]#234
renovate[bot] wants to merge 1 commit intodevelopfrom
renovate/pypi-aiohttp-vulnerability

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@renovate renovate bot commented Apr 1, 2026

This PR contains the following updates:

Package Change Age Confidence
aiohttp 3.13.33.13.4 age confidence

GitHub Vulnerability Alerts

CVE-2026-22815

Summary

Insufficient restrictions in header/trailer handling could cause uncapped memory usage.

Impact

An application could cause memory exhaustion when receiving an attacker controlled request or response. A vulnerable web application could mitigate these risks with a typical reverse proxy configuration.


Patch: aio-libs/aiohttp@0c2e9da

CVE-2026-34513

Summary

An unbounded DNS cache could result in excessive memory usage possibly resulting in a DoS situation.

Impact

If an application makes requests to a very large number of hosts, this could cause the DNS cache to continue growing and slowly use excessive amounts of memory.


Patch: aio-libs/aiohttp@c4d77c3

CVE-2026-34514

Summary

An attacker who controls the content_type parameter in aiohttp could use this to inject extra headers or similar exploits.

Impact

If an application allows untrusted data to be used for the multipart content_type parameter when constructing a request, an attacker may be able to manipulate the request to send something other than what the developer intended.


Patch: aio-libs/aiohttp@9a6ada9

CVE-2026-34515

Summary

On Windows the static resource handler may expose information about a NTLMv2 remote path.

Impact

If an application is running on Windows, and using aiohttp's static resource handler (not recommended in production), then it may be possible for an attacker to extract the hash from an NTLMv2 path and then extract the user's credentials from there.


Patch: aio-libs/aiohttp@0ae2aa0

CVE-2026-34516

Summary

A response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vulnerability.

Impact

Multipart headers were not subject to the same size restrictions in place for normal headers, potentially allowing substantially more data to be loaded into memory than intended. However, other restrictions in place limit the impact of this vulnerability.


Patch: aio-libs/aiohttp@8a74257

CVE-2026-34519

Summary

An attacker who controls the reason parameter when creating a Response may be able to inject extra headers or similar exploits.

Impact

In the unlikely situation that an application allows untrusted data to be used in the response's reason parameter, then an attacker could manipulate the response to send something different from what the developer intended.


Patch: aio-libs/aiohttp@53b35a2

CVE-2026-34517

Summary

For some multipart form fields, aiohttp read the entire field into memory before checking client_max_size.

Impact

If an application uses Request.post() an attacker can send a specially crafted multipart request to force significant temporary memory allocation even when the request is ultimately rejected.


Patch: aio-libs/aiohttp@cbb774f

CVE-2026-34518

Summary

When following redirects to a different origin, aiohttp drops the Authorization header, but retains the Cookie and Proxy-Authorization headers.

Impact

The Cookie and Proxy-Authorizations headers could contain sensitive information which may be leaked to an unintended party after following a redirect.


Patch: aio-libs/aiohttp@5351c98

CVE-2026-34520

Summary

The C parser (the default for most installs) accepted null bytes and control characters is response headers.

Impact

An attacker could send header values that are interpreted differently than expected due to the presence of control characters. For example, request.url.origin() may return a different value than the raw Host header, or what a reverse proxy interpreted it as., potentially resulting in some kind of security bypass.


Patch: aio-libs/aiohttp@9370b97

CVE-2026-34525

Summary

Multiple Host headers were allowed in aiohttp.

Impact

Mostly this doesn't affect aiohttp security itself, but if a reverse proxy is applying security rules depending on the target Host, it is theoretically possible that the proxy and aiohttp could process different host names, possibly resulting in bypassing a security check on the proxy and getting a request processed by aiohttp in a privileged sub app when using Application.add_domain().


Patch: aio-libs/aiohttp@e00ca3c
Patch: aio-libs/aiohttp@53e2e6f


Release Notes

aio-libs/aiohttp (aiohttp)

v3.13.4

Compare Source

===================

Features

  • Added max_headers parameter to limit the number of headers that should be read from a response -- by :user:Dreamsorcerer.

    Related issues and pull requests on GitHub:
    :issue:11955.

  • Added a dns_cache_max_size parameter to TCPConnector to limit the size of the cache -- by :user:Dreamsorcerer.

    Related issues and pull requests on GitHub:
    :issue:12106.

Bug fixes

  • Fixed server hanging indefinitely when chunked transfer encoding chunk-size
    does not match actual data length. The server now raises
    TransferEncodingError instead of waiting forever for data that will
    never arrive -- by :user:Fridayai700.

    Related issues and pull requests on GitHub:
    :issue:10596.

  • Fixed access log timestamps ignoring daylight saving time (DST) changes. The
    previous implementation used :py:data:time.timezone which is a constant and
    does not reflect DST transitions -- by :user:nightcityblade.

    Related issues and pull requests on GitHub:
    :issue:11283.

  • Fixed RuntimeError: An event loop is running error when using aiohttp.GunicornWebWorker
    or aiohttp.GunicornUVLoopWebWorker on Python >=3.14.
    -- by :user:Tasssadar.

    Related issues and pull requests on GitHub:
    :issue:11701.

  • Fixed :exc:ValueError when creating a TLS connection with ClientTimeout(total=0) by converting 0 to None before passing to ssl_handshake_timeout in :py:meth:asyncio.loop.start_tls -- by :user:veeceey.

    Related issues and pull requests on GitHub:
    :issue:11859.

  • Restored :py:meth:~aiohttp.BodyPartReader.decode as a synchronous method
    for backward compatibility. The method was inadvertently changed to async
    in 3.13.3 as part of the decompression bomb security fix. A new
    :py:meth:~aiohttp.BodyPartReader.decode_iter method is now available
    for non-blocking decompression of large payloads using an async generator.
    Internal aiohttp code uses the async variant to maintain security protections.

    Changed multipart processing chunk sizes from 64 KiB to 256KiB, to better
    match aiohttp internals
    -- by :user:bdraco and :user:Dreamsorcerer.

    Related issues and pull requests on GitHub:
    :issue:11898.

  • Fixed false-positive :py:class:DeprecationWarning for passing enable_cleanup_closed=True to :py:class:~aiohttp.TCPConnector specifically on Python 3.12.7.
    -- by :user:Robsdedude.

    Related issues and pull requests on GitHub:
    :issue:11972.

  • Fixed _sendfile_fallback over-reading beyond requested count -- by :user:bysiber.

    Related issues and pull requests on GitHub:
    :issue:12096.

  • Fixed digest auth dropping challenge fields with empty string values -- by :user:bysiber.

    Related issues and pull requests on GitHub:
    :issue:12097.

  • ClientConnectorCertificateError.os_error no longer raises :exc:AttributeError
    -- by :user:themylogin.

    Related issues and pull requests on GitHub:
    :issue:12136.

  • Adjusted pure-Python request header value validation to align with RFC 9110 control-character handling, while preserving lax response parser behavior, and added regression tests for Host/header control-character cases.
    -- by :user:rodrigobnogueira.

    Related issues and pull requests on GitHub:
    :issue:12231.

  • Rejected duplicate singleton headers (Host, Content-Type,
    Content-Length, etc.) in the C extension HTTP parser to match
    the pure Python parser behaviour, preventing potential host-based
    access control bypasses via parser differentials
    -- by :user:rodrigobnogueira.

    Related issues and pull requests on GitHub:
    :issue:12240.

  • Aligned the pure-Python HTTP request parser with the C parser by splitting
    comma-separated and repeated Connection header values for keep-alive,
    close, and upgrade handling -- by :user:rodrigobnogueira.

    Related issues and pull requests on GitHub:
    :issue:12249.

Improved documentation

  • Documented :exc:asyncio.TimeoutError for WebSocketResponse.receive()
    and related methods -- by :user:veeceey.

    Related issues and pull requests on GitHub:
    :issue:12042.

Packaging updates and notes for downstreams

  • Upgraded llhttp to 3.9.1 -- by :user:Dreamsorcerer.

    Related issues and pull requests on GitHub:
    :issue:12069.

Contributor-facing changes

  • The benchmark CI job now runs only in the upstream repository -- by :user:Cycloctane.

    It used to always fail in forks, which this change fixed.

    Related issues and pull requests on GitHub:
    :issue:11737.

  • Fixed flaky performance tests by using appropriate fixed thresholds that account for CI variability -- by :user:rodrigobnogueira.

    Related issues and pull requests on GitHub:
    :issue:11992.

Miscellaneous internal changes

  • Fixed test_invalid_idna to work with idna 3.11 by using an invalid character (\u0080) that is rejected by yarl during URL construction -- by :user:rodrigobnogueira.

    Related issues and pull requests on GitHub:
    :issue:12027.

  • Fixed race condition in test_data_file on Python 3.14 free-threaded builds -- by :user:rodrigobnogueira.

    Related issues and pull requests on GitHub:
    :issue:12170.



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