VulnerabilityPublished 21 Aug 2025

CVE-2025-9308: yarnpkg Yarn · ReDoS

Affects yarnpkg YarnSource CVE Database V5

Not known to be exploited · CVSS 4.8 Medium · end of life, no fix coming : replace or isolate yarnpkg Yarn; no fix will be released.

Data as of 26 Oct 2026, 11:42 UTC

CVSS 4.0 base score

4.8Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: None coming – the product is end of life

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

Attack Vector: Local
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
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: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
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: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
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 21 Aug 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

No fix will be released: yarnpkg Yarn is end of life. Replace it, or isolate it from untrusted networks until you can.

Affected software

Product	Affected	Fixed in
yarnpkg Yarn	Affected 1.22.0 – 1.22.22 23 affected builds	Fixed in–

AI-suggested

European organizations should prioritize upgrading to supported Yarn versions beyond 1.22.22, as these versions are no longer maintained and thus vulnerable. If upgrading is not immediately feasible, organizations should restrict local access to developer and build systems running vulnerable Yarn versions, enforcing strict access controls and monitoring for suspicious activity. Implementing endpoint protection and behavior-based anomaly detection can help identify attempts to exploit inefficient regex processing. Additionally, organizations can review and limit the use of untrusted input in Yarn configuration or scripts that might trigger the vulnerable code path. Incorporating Yarn usage into software supply chain security policies and ensuring build environments are isolated and hardened will reduce risk. Finally, organizations should maintain up-to-date inventories of development tools and dependencies to quickly identify and remediate unsupported or vulnerable components.

Description

A vulnerability has been found in yarnpkg Yarn up to 1.22.22. This impacts the function setOptions of the file src/util/request-manager.js. Such manipulation leads to inefficient regular expression complexity. Local access is required to approach this attack. This vulnerability only affects products that are no longer supported by the maintainer.

Impact

For European organizations, the impact of CVE-2025-9308 is primarily related to service availability and operational stability. Yarn is widely used in software development environments for managing JavaScript dependencies, especially in web and application development. Organizations relying on outdated Yarn versions may face denial of service conditions on developer machines or build servers if an attacker with local access triggers the inefficient regex processing. This could delay development cycles, continuous integration/continuous deployment (CI/CD) pipelines, and potentially impact production deployment timelines. While the vulnerability requires local access, insider threats or compromised developer workstations could exploit this to disrupt operations. The lack of vendor support for these versions means no official patches are available, forcing organizations to either upgrade to supported versions or implement workarounds. The impact is less severe on production runtime environments unless Yarn is used there, but the disruption in development and build environments can have cascading effects on software delivery and security patching processes.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 21 Aug 2025, 16:33 UTC

Technical details

References

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