VulnerabilityPublished 4 Feb 2026

CVE-2026-25537: Keats jsonwebtoken · Type Confusion

Affects Keats jsonwebtokenSource CVE Database V5

Public exploit available · CVSS 5.5 Medium : upgrade to 10.3.0 as a priority.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 4.0 base score

5.5Medium

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 42% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 10.3.0

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

Base metrics

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

Threat metrics

Exploit Maturity: POC

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: 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: 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: 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: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within 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.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: evidence found.
CVSS exploit maturity: proof of concept public
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), CVSS vector, 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 jsonwebtoken and github/Keats/jsonwebtoken to 10.3.0.

Affected software

Product	Affected	Fixed in
Keatsjsonwebtoken	Affected <10.3.0	Fixed in 10.3.0
crates.iogithub/Keats/jsonwebtoken`pkg:cargo/github/Keats/jsonwebtoken`Other threats	Affected <10.3.0	Fixed in 10.3.0

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

AI-suggested

Upgrade all instances of the jsonwebtoken Rust library to version 10.3.0 or later, where the vulnerability is patched.
Review and update JWT validation configurations to explicitly mark critical claims such as 'nbf' and 'exp' as required in the 'required_spec_claims' list to ensure malformed claims do not bypass validation.
Implement additional application-level validation for JWT claims to detect and reject tokens with incorrect claim types before they reach the jsonwebtoken library.
Conduct code audits and dependency scans to identify all usages of vulnerable jsonwebtoken versions across the organization’s codebase and container images.
Monitor authentication logs for anomalies indicative of token misuse, such as usage outside expected time windows.
Educate developers on secure JWT handling practices, emphasizing strict claim validation and type checking.
Employ runtime application self-protection (RASP) or web application firewalls (WAF) with JWT inspection capabilities to detect and block suspicious tokens.
Establish a patch management process to promptly apply security updates for third-party libraries.

Description

CVE-2026-25537 is a medium severity type confusion vulnerability in the Rust jsonwebtoken library versions prior to 10.3.0. The flaw arises from improper handling of standard JWT claims like 'nbf' or 'exp' when they are provided with incorrect JSON types, causing the library to treat malformed claims as absent. This leads to bypassing critical time-based validations such as 'Not Before' checks, potentially allowing attackers to circumvent authentication and authorization controls. The vulnerability does not require authentication or user interaction and can be exploited remotely. It has been patched in version 10.3.0. European organizations using affected versions of jsonwebtoken in their Rust applications, especially those relying on JWT for security, are at risk.

Impact

For European organizations, this vulnerability can undermine the security of systems that rely on JWTs for access control, session management, or API authentication. Attackers exploiting this flaw can bypass critical time-based restrictions, potentially gaining unauthorized access to protected resources or services. This could lead to data breaches, unauthorized transactions, or privilege escalation. Industries with stringent security requirements such as finance, healthcare, and government services are particularly at risk. The impact is exacerbated in environments where tokens are not tightly controlled or where the jsonwebtoken library is used in microservices architectures, increasing the attack surface. Additionally, the vulnerability could facilitate lateral movement within networks if attackers use compromised tokens to access internal services. Given the medium CVSS score of 5.5 and the lack of required authentication for exploitation, the threat is significant but not critical. However, the absence of user interaction and the potential for remote exploitation make timely mitigation essential to prevent abuse.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Feb 2026, 07:28 UTC

WeaknessesCWE-843

Technical details

References

Community reviews

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