CVE-2025-59936VulnerabilityPublished 27 Sep 2025Updated 29 Sep 2025

CVE-2025-59936: nearform get-jwks · Improper Encoding or Escaping of Output

Affects nearform get-jwksSource CVE Database V5

Not known to be exploited · CVSS 9.4 Critical : upgrade to 11.0.2 as a priority.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.0 base score

9.4Critical

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 11.0.2

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 27 Sep 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 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 nearform get-jwks to 11.0.2.

Affected software

Product	Affected	Fixed in
nearform get-jwks	Affected <11.0.2	Fixed in 11.0.2

AI-suggested

European organizations should urgently upgrade all instances of the 'get-jwks' library to version 11.0.2 or later, where the vulnerability is patched. Beyond upgrading, organizations should audit their JWT validation workflows to ensure that issuer (iss) claim validation occurs before or during key retrieval, not after, to prevent cache poisoning attacks. Implementing strict validation logic that tightly couples keys to their issuers and avoids shared caches across different issuers can mitigate risks. Additionally, organizations should consider deploying runtime monitoring and anomaly detection on JWT validation failures or unusual token usage patterns. Employing defense-in-depth by validating tokens at multiple layers, including API gateways and identity providers, can reduce exposure. Regularly reviewing and updating dependencies, combined with automated vulnerability scanning in CI/CD pipelines, will help prevent similar issues. Finally, organizations should review their incident response plans to quickly address any detected misuse of JWTs and notify affected stakeholders as required by GDPR and other regulations.

Description

get-jwks contains fetch utils for JWKS keys. In versions prior to 11.0.2, a vulnerability in get-jwks can lead to cache poisoning in the JWKS key-fetching mechanism. When the iss (issuer) claim is validated only after keys are retrieved from the cache, it is possible for cached keys from an unexpected issuer to be reused, resulting in a bypass of issuer validation. This design flaw enables a potential attack where a malicious actor crafts a pair of JWTs, the first one ensuring that a chosen public key is fetched and stored in the shared JWKS cache, and the second one leveraging that cached key to pass signature validation for a targeted iss value. The vulnerability will work only if the iss validation is done after the use of get-jwks for keys retrieval. This issue has been patched in version 11.0.2.

Impact

For European organizations, this vulnerability poses a significant risk to the integrity and confidentiality of authentication and authorization processes that rely on JWTs validated using the 'get-jwks' library. Many modern web applications, APIs, and microservices use JWTs for stateless authentication and authorization, often fetching public keys dynamically from trusted issuers via JWKS endpoints. Exploitation of this vulnerability could allow attackers to impersonate legitimate users or services by forging JWTs that pass signature validation despite originating from untrusted issuers. This could lead to unauthorized access to sensitive data, privilege escalation, and potential lateral movement within networks. Given the critical nature of JWTs in identity and access management, the impact extends to compliance risks under GDPR and other data protection regulations if personal or sensitive data is exposed or manipulated. Additionally, organizations in sectors such as finance, healthcare, and government, which heavily rely on secure token validation, could face operational disruptions and reputational damage. The vulnerability's network-exploitable nature means that exposed APIs or services using vulnerable 'get-jwks' versions are at immediate risk, especially if they do not implement additional issuer validation safeguards outside the library.

Summary

CVE-2025-59936 is a critical vulnerability affecting versions of the nearform 'get-jwks' library prior to 11.0.2. The 'get-jwks' library is used to fetch JSON Web Key Sets (JWKS) for JWT signature verification. The vulnerability arises from a design flaw in the caching mechanism of JWKS keys. Specifically, the library caches keys fetched from issuers but performs issuer (iss) claim validation only after retrieving keys from the cache. This sequence allows an attacker to perform cache poisoning by first injecting a malicious public key into the shared JWKS cache associated with one issuer, and then leveraging that cached key to validate a JWT from a different, targeted issuer. This bypasses the intended issuer validation, enabling signature validation to succeed with a key that should not be trusted for that issuer. The attack requires no authentication or user interaction and can be executed remotely over the network, making exploitation relatively straightforward. The vulnerability is classified under CWE-116 (Improper Encoding or Escaping of Output), indicating issues with how output data is handled, which in this context relates to the improper handling of cached keys and issuer validation order. The flaw has been addressed in version 11.0.2 of 'get-jwks'. The CVSS v3.0 base score is 9.4 (critical), reflecting high impact on confidentiality and integrity with low attack complexity and no privileges or user interaction required. No known exploits are currently reported in the wild, but the severity and ease of exploitation make this a high-risk vulnerability for any systems relying on vulnerable versions of 'get-jwks' for JWT validation.

CWE-116Improper Encoding or Escaping of Output (opens in a new tab)
Class weaknessLikelihood of exploit: HighOWASP Top 10 A05:2025: Injection (opens in a new tab)
The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Parameterization
If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.
Architecture and Design · Implementation
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
OWASP Cheat Sheets
Content Security Policy (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
Query Parameterization (opens in a new tab)
OWASP ASVS 4.0.3
V14.4.6 (opens in a new tab)
V14.4.4 (opens in a new tab)
V14.4.2 (opens in a new tab)
Attack patterns
Cross Zone Scripting (opens in a new tab)
User-Controlled Filename (opens in a new tab)
Web Server Logs Tampering (opens in a new tab)
AJAX Footprinting (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Oct 2025, 00:57 UTC

WeaknessesCWE-116

Technical details

References

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