CVE-2023-38709VulnerabilityPublished 4 Apr 2024Updated 4 Nov 2025

CVE-2023-38709: Apache HTTP Server · HTTP response splitting

Affects Apache HTTP ServerSource CVE Database V5

Not known to be exploited · CVSS 7.3 High : upgrade to 2.4.59 soon.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.3High

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

EPSS: 3.9% chance of exploitation in 30 days – higher than 90% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.4.59

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

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

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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
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 on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Apr 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 2026-10-25.

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 apache/httpd to 2.4.59.

Affected software

Product	Affected	Fixed in
Apacheapache/httpd`pkg:rpm/apache/httpd`Other threats	Affected <2.4.59	Fixed in 2.4.59

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

AI-suggested

1. Monitor Apache Software Foundation advisories closely and apply official patches immediately once released for versions up to 2.4.58. 2. If you cannot patch yet, implement strict input validation and sanitization on backend systems and content generators to prevent injection of CRLF characters into HTTP headers. 3. Deploy Web Application Firewalls (WAFs) configured to detect and block HTTP response splitting attempts by inspecting HTTP headers for suspicious characters or sequences. 4. Review and harden server and application configurations to minimize exposure of vulnerable endpoints and reduce attack surface. 5. Conduct regular security assessments and penetration testing focused on HTTP header injection and response splitting vectors. 6. Educate development and operations teams about secure coding practices related to HTTP header handling. 7. Utilize network-level protections such as intrusion detection/prevention systems (IDS/IPS) to identify anomalous HTTP traffic patterns. 8. Consider implementing Content Security Policy (CSP) headers to mitigate the impact of potential XSS attacks resulting from response splitting.

Description

Faulty input validation in the core of Apache allows malicious or exploitable backend/content generators to split HTTP responses. This issue affects Apache HTTP Server: through 2.4.58.

Impact

For European organizations, the impact of CVE-2023-38709 can be substantial due to the extensive use of Apache HTTP Server in web hosting, enterprise applications, and government infrastructure. Successful exploitation can lead to manipulation of HTTP responses, enabling attackers to poison web caches, inject malicious scripts, hijack user sessions, or redirect users to malicious sites. This compromises confidentiality by exposing sensitive information, integrity by altering content delivered to users, and availability by potentially disrupting web services. Organizations handling sensitive personal data under GDPR may face regulatory and reputational consequences if this vulnerability is exploited. Additionally, sectors such as finance, healthcare, and public administration, which rely heavily on web services, could experience operational disruptions and data breaches. The lack of authentication and user interaction requirements lowers the barrier for attackers, increasing the likelihood of exploitation if unpatched. The absence of known exploits in the wild currently provides a window for proactive defense, but the risk remains high given the vulnerability's nature and Apache's market penetration.

CWE-1284Improper Validation of Specified Quantity in Input (opens in a new tab)
Base weakness
The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2025, 21:37 UTC

WeaknessesCWE-1284

Technical details

References

Community reviews

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