CVE-2025-69225VulnerabilityPublished 5 Jan 2026

CVE-2025-69225: aio-libs aiohttp · HTTP Request/Response Smuggling

Affects aio-libs aiohttpSource CVE Database V5

Not known to be exploited · CVSS 2.7 Low : upgrade to 3.13.3 when convenient.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 4.0 base score

2.7Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.13.3

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: Unreported

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: Unreported: Based on threat intelligence sources each of the following must apply: · No knowledge of publicly available proof-of-concept · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 5 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade aio-libs aiohttp to 3.13.3.

Affected software

Product	Affected	Fixed in
aio-libsaiohttp	Affected <3.13.3	Fixed in 3.13.3
PyPIaiohttp`pkg:pypi/aiohttp`Other threats	Affected <3.13.3	Fixed in 3.13.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

The definitive mitigation is to upgrade all aiohttp deployments to version 3.13.3 or later, where the vulnerability is fixed. Organizations should audit their Python environments to identify usage of aiohttp versions below 3.13.3, including indirect dependencies in container images and serverless functions. Implementing strict input validation and HTTP header sanitization at the web application firewall (WAF) or reverse proxy level can provide additional defense-in-depth against malformed Range headers. Monitoring HTTP traffic for anomalous Range header values or request desynchronization symptoms can help detect attempted exploitation. Network segmentation and limiting exposure of aiohttp-based services to trusted networks reduce attack surface. Finally, maintaining an up-to-date inventory of asynchronous Python services and integrating vulnerability scanning into CI/CD pipelines will prevent future exposure.

Description

CVE-2025-69225 is a low-severity HTTP request smuggling vulnerability in aio-libs aiohttp versions prior to 3.13.3. It arises from the parser allowing non-ASCII decimal characters in the HTTP Range header, potentially enabling inconsistent interpretation of HTTP requests. Although no known exploits or impacts have been reported, this flaw could theoretically be leveraged to smuggle HTTP requests, leading to request desynchronization between front-end and back-end servers. The vulnerability is fixed in aiohttp 3.13.3. European organizations using vulnerable aiohttp versions in asynchronous Python web services should upgrade promptly to mitigate risk. Given the low CVSS score and lack of known exploits, the threat is currently low but should not be ignored in sensitive environments.

Impact

For European organizations, the primary impact is the potential for HTTP request smuggling attacks against web services built on vulnerable aiohttp versions. Such attacks could lead to unauthorized request execution, session hijacking, cache poisoning, or bypassing of security controls, undermining confidentiality and integrity. However, given the low severity and lack of known exploits, the immediate risk is minimal. Organizations running aiohttp-based asynchronous web applications, especially those exposed to the internet or handling sensitive data, could face targeted attacks if threat actors discover reliable exploitation methods. The impact would be more pronounced in sectors with high reliance on Python asyncio frameworks, such as fintech, e-commerce, and cloud service providers. Disruption of web services or data leakage could have regulatory and reputational consequences under GDPR and other European data protection laws.

Summary

CVE-2025-69225 identifies a vulnerability in the aiohttp framework, an asynchronous HTTP client/server library widely used in Python asyncio applications. Versions 3.13.2 and earlier contain a parsing logic flaw in handling the HTTP Range header, where the parser permits non-ASCII decimal characters. This can cause inconsistent interpretation of HTTP requests between different components (e.g., proxies, load balancers, and backend servers), a classic setup for HTTP request smuggling (CWE-444). HTTP request smuggling exploits discrepancies in how HTTP requests are parsed, allowing attackers to craft malicious requests that bypass security controls, poison caches, or hijack user sessions. Although no concrete exploit or impact has been demonstrated for this specific flaw, the theoretical risk remains due to the nature of request smuggling attacks. The vulnerability requires no authentication, no user interaction, and can be triggered remotely over the network, but the complexity of exploitation and the low CVSS score (2.7) indicate limited immediate risk. The issue is resolved in aiohttp version 3.13.3, which corrects the parser behavior to reject non-ASCII decimals in the Range header, thus preventing inconsistent request interpretation.

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') (opens in a new tab)
Base weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
Implementation
Use a web server that employs a strict HTTP parsing procedure, such as Apache.
Implementation
Use only SSL communication.
Implementation
Terminate the client session after each request.
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
REST Security (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V13.2.5 (opens in a new tab)
Attack patterns
HTTP Response Smuggling (opens in a new tab)
HTTP Request Smuggling (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Jan 2026, 01:01 UTC

WeaknessesCWE-444

Technical details

References

Community reviews

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