CVE-2024-2757VulnerabilityPublished 14 May 2024Updated 4 Nov 2025

CVE-2024-2757: PHP · Vulnerability

Affects PHPSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 8.3.5 soon.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 1.9% chance of exploitation in 30 days – higher than 79% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 8.3.5

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

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 May 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 php/php-src to 8.3.5.

Affected software

Product	Affected	Fixed in
GitHubphp/php-src`pkg:github/php/php-src`Other threats	Affected <8.3.5 >=8.3.0	Fixed in 8.3.5

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

AI-suggested

1. Upgrade PHP to version 8.3.5 or later as soon as it is released by the PHP Group, since this will contain the official fix for the vulnerability. 2. In the interim, implement input validation and sanitization to detect and block unusually long strings of non-space characters followed by a space in inputs processed by mb_encode_mimeheader(). 3. Employ web application firewalls (WAFs) with custom rules to detect and mitigate suspicious payloads targeting this function. 4. Monitor application logs and network traffic for signs of repeated or anomalous requests that could indicate exploitation attempts. 5. Limit exposure of PHP-based services to the internet where possible, using network segmentation and access controls. 6. Conduct code reviews to identify any direct or indirect usage of mb_encode_mimeheader() and assess if alternative encoding methods can be used temporarily. 7. Prepare incident response plans for potential DoS attacks, including resource scaling and failover strategies. 8. Stay informed via official PHP security announcements and CVE databases to apply patches promptly.

Description

In PHP 8.3.* before 8.3.5, function mb_encode_mimeheader() runs endlessly for some inputs that contain long strings of non-space characters followed by a space. This could lead to a potential DoS attack if a hostile user sends data to an application that uses this function.

Impact

For European organizations, this vulnerability poses a significant risk to the availability of web services running PHP 8.3.*. Many European enterprises, government agencies, and service providers rely on PHP for web applications, including content management systems, e-commerce platforms, and internal tools. An attacker exploiting this flaw can cause denial of service by sending specially crafted requests, potentially leading to downtime, degraded user experience, and loss of business continuity. Critical sectors such as finance, healthcare, and public administration could face operational disruptions. Additionally, the vulnerability could be leveraged as part of a larger attack chain or to distract security teams while other attacks are carried out. Since no authentication or user interaction is needed, the attack surface is broad, affecting any exposed PHP-based service. The absence of known exploits currently provides a window for proactive mitigation, but the high CVSS score indicates that exploitation could be straightforward once exploit code becomes available. The impact on confidentiality and integrity is negligible, but the availability impact is high, which is critical for service reliability in European markets.

CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (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, 17:52 UTC

WeaknessesCWE-400

Technical details

References

Community reviews

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