Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
CVE-2026-40496 is a high-severity Use of Insufficiently Random Values (CWE-330) vulnerability in Freescout Freescout. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Forge Web Credentials (T1606); ranked at the 33th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SC-12 (Cryptographic Key Establishment and Management) — 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-2026-40496 is a high-severity vulnerability in FreeScout, an open-source self-hosted help desk and shared mailbox application. In versions prior to 1.8.213, the attachment download tokens are generated using a weak and predictable formula: MD5(APP_KEY + attachment_id + size). This design flaw allows tokens to be forged because attachment IDs are sequential integers and file sizes fall within a small brute-forceable range, enabling unauthorized access to private attachments.
An unauthenticated attacker can exploit this vulnerability remotely with low complexity and no privileges, as indicated by the CVSS 3.1 base score of 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N). By guessing or enumerating attachment IDs and sizes, the attacker crafts valid tokens to download any private attachment without valid credentials, resulting in high impacts on confidentiality and integrity but no availability disruption. Associated CWEs include CWE-330 (Use of Insufficiently Random Values) and CWE-340 (Generation of Predictable Numbers or Identifiers).
The FreeScout security advisory (GHSA-2783-wxmm-wmwr) and release notes for version 1.8.213 detail the fix implemented via commit dbdf8f2260b43a21818255c70f0b61b9de9cd555, which strengthens token generation to prevent prediction. Security practitioners should upgrade to FreeScout 1.8.213 or later to mitigate the issue, and review exposed instances for potential token forgery attempts.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24049
Vulnerability Data
FreeScout is a free self-hosted help desk and shared mailbox. Prior to version 1.8.213, attachment download tokens are generated using a weak and predictable formula: `md5(APP_KEY + attachment_id + size)`. Since attachment_id is sequential and size can be brute-forced in…
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a small range, an unauthenticated attacker can forge valid tokens and download any private attachment without credentials. Version 1.8.213 fixes the issue.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 14 hardening rules · 5 OS baselines
V11.3.4
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover predictable number generation through targeted analysis or fuzzing of identifier creation routines.
SC-12 requires proper cryptographic key establishment and management, which structurally mandates use of sufficient randomness for key generation.
Authenticator management requires secure initial distribution and handling of authenticators, structurally preventing predictable values from being usable.
SC-13 requires selection and implementation of approved cryptographic algorithms and methods, which inherently depend on and enforce sufficiently random values.
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 SDLC practices directly enforce use of cryptographically strong RNGs and catch insufficient randomness during design, coding, and testing.
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.
Cryptographic controls require use of approved, sufficiently random values for keys and nonces.
Security testing can detect weak randomness but does not prescribe the control itself.
Secure SDLC processes include verification steps that can catch insufficient randomness but do not directly specify RNG requirements.
Secure coding standards explicitly prohibit use of weak or predictable random number generators.
Secure authentication mechanisms depend on unpredictable values (nonces, salts, session tokens) to resist guessing.
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 (4 rules)
- V-248524 OL 8 must implement NIST FIPS-validated cryptography for the following: To provision digital signatures, to generate cryptographic hashes, and to protect data requiring data-at-rest protections in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards. prevents CWE-340
- V-248563 The OL 8 SSH server must be configured to use strong entropy. prevents CWE-330
- V-248599 OL 8 must enable the hardware random number generator entropy gatherer service. prevents CWE-330
Oracle Linux 9 (1 rule)
- V-271511 OL 9 must enable the hardware random number generator entropy gatherer service. prevents CWE-330
RHEL 7 (1 rule)
- V-204497 The Red Hat Enterprise Linux operating system must implement NIST FIPS-validated cryptography for the following: to provision digital signatures, to generate cryptographic hashes, and to protect data requiring data-at-rest protections in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards. prevents CWE-340
RHEL 8 (3 rules)
- V-244527 RHEL 8 must have the packages required to use the hardware random number generator entropy gatherer service. prevents CWE-330, CWE-340
- V-230253 RHEL 8 must ensure the SSH server uses strong entropy. prevents CWE-330
- V-230285 RHEL 8 must enable the hardware random number generator entropy gatherer service. prevents CWE-330
RHEL 9 (1 rule)
- V-257782 RHEL 9 must enable the hardware random number generator entropy gatherer service. prevents CWE-330