VulnerabilityPublished 1 Jul 2024Updated 26 Aug 2024

CVE-2024-39249: async · ReDoS

Affects asyncSource CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 26 Oct 2026, 11:07 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 56% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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 1 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 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 or the CVSS exploit maturity 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
npmasync`pkg:npm/async`Other threats	Affected <=2.6.4 <=3.2.5	Fixed in–

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

AI-suggested

Avoid using vulnerable Async versions (<= 2.6.4 and <= 3.2.5) in production environments, especially where input sources cannot be fully trusted.
Monitor official Async library repositories and security advisories for patches or updates addressing this vulnerability and apply them promptly once available.
Implement input validation and sanitization to restrict or sanitize inputs reaching the autoinject function to prevent maliciously crafted regex payloads.
Employ runtime resource limits such as CPU timeouts or regex execution timeouts to mitigate potential ReDoS impact.
Use Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) to detect and block suspicious input patterns targeting regex parsing.
Conduct code reviews and security testing focusing on regex usage in your codebase to identify and remediate similar ReDoS risks.
Consider isolating or sandboxing components that use vulnerable regexes to limit the blast radius of potential DoS attacks.
Maintain comprehensive monitoring and alerting on service performance metrics to detect early signs of DoS conditions.

Description

Async <= 2.6.4 and <= 3.2.5 are vulnerable to ReDoS (Regular Expression Denial of Service) while parsing function in autoinject function. NOTE: this is disputed by the supplier because there is no realistic threat model: regular expressions are not used with untrusted input.

Impact

The primary impact of CVE-2024-39249 is on the availability of systems using the affected Async library versions. Successful exploitation can cause denial of service by exhausting CPU resources through maliciously crafted input that triggers excessive regex backtracking. This can lead to service outages, degraded performance, and potential cascading failures in dependent systems. Organizations relying on Async in critical infrastructure, web services, or backend processing pipelines may experience downtime or degraded user experience. Although confidentiality and integrity are not directly affected, the availability disruption can have significant operational and reputational consequences. The lack of authentication or user interaction requirements increases the risk of remote exploitation. Since no known exploits are currently active, the threat is theoretical but should be treated seriously given the CVSS rating and potential impact on service continuity.

CWE-1333Inefficient Regular Expression Complexity (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
Architecture and Design
Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
System Configuration
Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
Implementation
Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
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
Regular Expression Exponential Blowup (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 28 Feb 2026, 04:21 UTC

WeaknessesCWE-1333

Technical details

References

Community reviews

Related threats