CVE-2026-35039
Nearform Fast-Jwt 0.1.0 – 6.1.0
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NSummary
CVE-2026-35039 is a critical-severity Insufficient Verification of Data Authenticity (CWE-345) vulnerability in Nearform Fast-Jwt. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Path Interception (T1034); ranked at the 12th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SC-23 (Session Authenticity) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-35039 affects the fast-jwt library, a fast JSON Web Token (JWT) implementation for Node.js applications, in versions from 0.0.1 up to but not including 6.2.0. The vulnerability arises when developers configure a custom cacheKeyBuilder method that fails to generate unique keys for different tokens, resulting in cache collisions during the JWT verification process. This leads to valid tokens being misidentified, where they return claims from other valid tokens, potentially causing user misidentification. The issue is rated with a CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N) and is associated with CWEs 345 (Insufficient Verification of Data Authenticity), 706 (Use of Incorrectly-Resolved Name Into a Reference), and 1289 (Improper Validation of Specified Type of Input).
An attacker can exploit this vulnerability remotely over the network with low complexity, no privileges, and no user interaction required. Exploitation requires the target application to use fast-jwt with a flawed custom cacheKeyBuilder implementation. By crafting JWTs that collide in the cache with legitimate tokens, an attacker can cause the verification process to associate incorrect claims with a presented valid token, enabling user impersonation or unauthorized access to another user's privileges and data. This impacts confidentiality and integrity highly but does not affect availability.
The GitHub security advisory (GHSA-rp9m-7r4c-75qg) and the patching commit (de121056c6415b58770c60640881eaec67ac4ceb) confirm that version 6.2.0 of fast-jwt resolves the issue by improving cache key generation to prevent collisions. Security practitioners should upgrade to 6.2.0 or later and review any custom cacheKeyBuilder implementations for proper uniqueness in key generation.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-19380
Vulnerability Data
fast-jwt provides fast JSON Web Token (JWT) implementation. From 0.0.1 to before 6.2.0, setting up a custom cacheKeyBuilder method which does not properly create unique keys for different tokens can lead to cache collisions. This could cause tokens to be…
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mis-identified during the verification process leading to valid tokens returning claims from different valid tokens and users being mis-identified as other users based on the wrong token. Version 6.2.0 contains a patch.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 8 hardening rules · 5 OS baselines
V5.2.2V9.1.3V10.4.6V2.2.2
Mitigating Controls (NIST 800-53 r5) AI
Explicit requirement to protect session authenticity structurally prevents the weakness for communications.
SI-10 requires validity checks on information inputs, directly stopping unsafe equivalence validation failures for identifiers and references.
Integrity verification tools detect (but do not stop) the acceptance of data lacking authenticity.
Access enforcement applies authorization checks to the resolved resource, blocking access outside the intended sphere.
Information flow enforcement can constrain flows that result from an incorrectly resolved name or reference.
Cryptographic mechanisms can be used to verify authenticity, thereby preventing acceptance of invalid data.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices directly prevent incorrect name/reference resolution bugs during coding.
CWE-345 directly impairs RC.RP-05's verification of restored-asset integrity/authenticity, largely defeating the outcome while still leaving other restoration-confirmation steps partially viable.
Enforced authorization boundaries limit damage from an incorrectly resolved reference.
Logical segmentation and access controls reduce the chance an out-of-sphere resolution succeeds.
Hardened configuration baselines can constrain allowable name-to-resource mappings.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect missing or weak data authenticity verification.
Network controls can enforce authenticated channels, reducing risk of accepting unauthentic data.
Secure network services often include authenticity checks for data exchanged over those services.
Segregated networks limit the blast radius when a name or reference resolves outside the intended control sphere.
Cryptographic mechanisms directly verify data origin and integrity, preventing acceptance of unauthentic data.
Secure SDLC incorporates authenticity verification requirements throughout development.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (2 rules)
- V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. prevents CWE-345
- V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-345
Oracle Linux 9 (1 rule)
- V-271525 OL 9 must have GPG signature verification enabled for all software repositories. prevents CWE-345
RHEL 7 (2 rules)
- V-204447 The Red Hat Enterprise Linux operating system must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-345
- V-204448 The Red Hat Enterprise Linux operating system must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-345
RHEL 8 (2 rules)
- V-230264 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-345
- V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-345
RHEL 9 (1 rule)
- V-257822 RHEL 9 must have GPG signature verification enabled for all software repositories. prevents CWE-345