GHSA-jg22-mg44-37j8 CVE-2026-34993 PYSEC-2026-2104

AIOHTTP is Vulnerable to Deserialization of Untrusted Data

High PyPI

Severity: 6.4 / 10; High · CVSS 3.1
Exploit chance (EPSS): 0.18%; Chance of exploitation in the next 30 days. Higher than 7.46% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-502 Deserialization of Untrusted Data
Fix: 3.14.0; Upgrade aiohttp to this version or later

Description

Summary

Using CookieJar.load() with untrusted input may allow arbitrary code execution.

Impact

Most applications using this function will be doing so with the user's own data, so this is unlikely to affect many applications.

Workaround

If an application does allow attacker controlled files to be loaded, a workaround on older releases would be to sanitise the files before loading.

Patch: https://github.com/aio-libs/aiohttp/commit/dcf40f30637e8752c76781cf6703b5a236749a00

Affected versions

PyPI

Package	Vulnerable	Fixed in
aiohttp	`< 3.14.0`	`3.14.0`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

aiohttp PyPI → `3.14.0`

pip

pip install --upgrade "aiohttp>=3.14.0"

poetry

poetry add "aiohttp>=3.14.0"

uv

uv add "aiohttp>=3.14.0"

Severity breakdown

CVSS 3.1 6.4

CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:C/C:L/I:H/A:L

Attack vector: Local
Attack complexity: High
Privileges required: High
User interaction: Required
Scope: Changed
Confidentiality: Low
Integrity: High
Availability: Low

Weakness

CWE-502: Deserialization of Untrusted Data

The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

How to prevent it

Architecture and Design, Implementation: If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
Implementation: When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
Implementation: Explicitly define a final object() to prevent deserialization.
Architecture and Design, Implementation: Make fields transient to protect them from deserialization. An attempt to serialize and then deserialize a class containing transient fields will result in NULLs where the transient data should be. This is an excellent way to prevent time, environment-based, or sensitive variables from being carried over and used improperly.
Implementation: Avoid having unnecessary types or gadgets (a sequence of instances and method invocations that can self-execute during the deserialization process, often found in libraries) available that can be leveraged for malicious ends. This limits the potential for unintended or unauthorized types and gadgets to be leveraged by the attacker. Add only acceptable classes to an allowlist. Note: new gadgets are constantly being discovered, so this alone is not a sufficient mitigation.
Architecture and Design, Implementation: Employ cryptography of the data or code for protection. However, it's important to note that it would still be client-side security. This is risky because if the client is compromised then the security implemented on the client (the cryptography) can be bypassed.
Operation: Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].

References

Advisories

Issue reports

bugzilla.redhat.com/show_bug.cgi

Packages

github.com/aio-libs/aiohttp

Timeline

Jun 2, 2026 Published
Sep 10, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-pqxq-w44r-73xw AIOHTTP: Pure-Python parser request smuggling	Medium	Also affects aiohttp
GHSA-gx76-c99x-2c96 AIOHTTP: Cookie from subdomain can remove Host-Only Scope from existing cookies	Low	Also affects aiohttp
GHSA-f9xw-jh8m-3mwq AIOHTTP: Absolute-form request targets can spoof Request.scheme	Medium	Also affects aiohttp
GHSA-9xw5-w5jj-pvcg AIOHTTP: File descriptor exhaustion in multipart requests	High	Also affects aiohttp
GHSA-6cjc-53gc-5rqm AIOHTTP: Connector pool exhaustion via Max-Age overflow	Medium	Also affects aiohttp
GHSA-5wr8-gcqf-gqf3 aiohttp server lacks an initial request/header timeout	High	Also affects aiohttp
GHSA-494j-54xm-rwp3 AIOHTTP: Secure attribute not enforced for shared cookie	Medium	Also affects aiohttp
GHSA-2g87-pp6c-29x5 aiohttp: Multiple instances of excessive or unbounded memory/CPU use	High	Also affects aiohttp

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