VulnerabilityPublished 28 May 2025

CVE-2025-3864: hackney · Missing Release of Resource after Effective Lifetime

Affects hackneySource CVE Database V5

Not known to be exploited · CVSS 2.3 Low : upgrade to 1.24.0 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 4.0 base score

2.3Low

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 58% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.24.0

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

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

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: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
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: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system 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 Vulnerable System 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 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.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 May 2025
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

Upgrade hackney to 1.24.0.

Affected software

Product	Affected	Fixed in
Hexhackney`pkg:hex/hackney`Other threats	Affected <1.24.0	Fixed in 1.24.0

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

AI-suggested

To mitigate CVE-2025-3864, European organizations should take the following specific actions: 1) Upgrade hackney to version 1.24.0 or later, where the resource release issue has been fixed. 2) Review and audit application dependencies to identify usage of hackney and ensure all instances are updated. 3) Implement connection pool monitoring and alerting to detect abnormal exhaustion patterns that could indicate exploitation attempts. 4) Employ rate limiting or filtering on incoming requests that could trigger excessive redirects to reduce the risk of resource exhaustion. 5) Conduct thorough testing of applications handling HTTP redirects to ensure proper resource management and graceful degradation under load. 6) Incorporate this vulnerability into incident response playbooks to quickly identify and respond to potential DoS conditions related to connection pool depletion. 7) Consider architectural adjustments such as increasing connection pool sizes or using alternative HTTP client libraries if immediate patching is not feasible, while planning for timely remediation.

Description

Hackney fails to properly release HTTP connections to the pool after handling 307 Temporary Redirect responses. Remote attackers can exploit this to exhaust connection pools, causing denial of service in applications using the library. Fix for this issue has been included in 1.24.0 release.

Impact

For European organizations, the primary impact of CVE-2025-3864 is the potential for denial of service in applications that utilize the hackney HTTP client library. This can disrupt business operations, particularly for services that depend on stable and reliable HTTP communications, such as web services, APIs, and microservices architectures. Organizations in sectors like finance, healthcare, telecommunications, and government, which often rely on robust backend communication libraries, may experience service outages or degraded performance if the vulnerability is exploited. Although the severity is rated low, the operational impact can be significant in environments with high traffic or where service availability is critical. Additionally, the exploitation does not require authentication, increasing the risk from external attackers. The vulnerability could be leveraged as part of a broader attack chain to cause service disruption or to distract from other malicious activities. European organizations with compliance obligations around service availability and incident response should prioritize patching to maintain operational resilience.

CWE-772Missing Release of Resource after Effective Lifetime (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
It is good practice to be responsible for freeing all resources you allocate and to be consistent with how and where you free resources in a function. If you allocate resources that you intend to free upon completion of the function, you must be sure to free the resources at all exit points for that function including…
Operation · Architecture and Design · Resource Limitation
Use resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available.
Attack patterns
HTTP DoS (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 6 Jul 2025, 01:42 UTC

WeaknessesCWE-772

Technical details

References

Community reviews

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