CVE-2024-35161VulnerabilityPublished 26 Jul 2024Updated 3 Nov 2025

CVE-2024-35161: Apache Traffic Server · HTTP Request Smuggling

Affects Apache Traffic ServerSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical · fixed in 8.1.11 : patch Apache Traffic Server as a priority.

Data as of 26 Oct 2026, 07:57 UTC

CVSS 3.1 base score

9.1Critical

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

EPSS: 0.9% chance of exploitation in 30 days – higher than 61% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 8.1.11

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: None

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 26 Jul 2024
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 2026-10-26.

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

Affected software

Product	Affected	Fixed in
Apache Software Foundation Apache Traffic Server	Affected =8.0.0 =9.0.0	Fixed in–

AI-suggested

European organizations should immediately upgrade Apache Traffic Server to versions 8.1.11 or 9.2.5 where the vulnerability is fixed. Until upgrades can be applied, administrators should enable the proxy.config.http.drop_chunked_trailers setting to prevent forwarding of chunked trailer sections, reducing the attack surface. Conduct thorough audits of all proxy and caching configurations to ensure no legacy or custom modules reintroduce similar parsing inconsistencies. Implement strict input validation and HTTP request normalization on both proxy and origin servers to detect and block malformed requests. Monitor web traffic for anomalies indicative of request smuggling attempts, such as unexpected request lengths or header inconsistencies. Employ layered security controls including web application firewalls configured to detect HTTP request smuggling patterns. Regularly review and update incident response plans to include scenarios involving HTTP request smuggling and cache poisoning. Finally, maintain up-to-date inventories of all Apache Traffic Server deployments to ensure timely patch management and vulnerability tracking.

Description

Apache Traffic Server forwards malformed HTTP chunked trailer section to origin servers. This can be utilized for request smuggling and may also lead cache poisoning if the origin servers are vulnerable. This issue affects Apache Traffic Server: from 8.0.0 through 8.1.10, from 9.0.0 through 9.2.4. Users can set a new setting (proxy.config.http.drop_chunked_trailers) not to forward chunked trailer section. Users are recommended to upgrade to version 8.1.11 or 9.2.5, which fixes the issue.

Impact

For European organizations, this vulnerability poses a significant risk to web infrastructure relying on Apache Traffic Server as a reverse proxy or caching server. Successful exploitation can lead to unauthorized request injection, bypassing security controls such as web application firewalls or authentication mechanisms. This can compromise the confidentiality of sensitive data by exposing internal requests or enabling session hijacking. Integrity is threatened through cache poisoning, where malicious or altered content is served to users, potentially spreading malware or misinformation. Availability impact is limited but may occur if backend servers become unstable due to malformed requests. Given the critical CVSS score and the lack of required authentication, attackers can remotely exploit this vulnerability at scale. Organizations in sectors such as finance, government, healthcare, and telecommunications, which heavily rely on secure and reliable web services, are particularly at risk. The vulnerability also undermines trust in web services and can lead to regulatory compliance issues under GDPR if personal data is exposed or manipulated.

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 4 Nov 2025, 00:02 UTC

WeaknessesCWE-444

Technical details

References

Community reviews

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