CVE-2026-93483
Raw vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L/E:X/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:Y/R:U/V:X/RE:L/U:RedCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-93483 is a critical-severity Use of Less Trusted Source (CWE-348) vulnerability in Znuny (inferred from references). Its CVSS base score is 9.5 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Cached Domain Credentials (T1003.005); ranked at the 13th 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 AC-4 (Information Flow Enforcement) and IA-3 (Device Identification and Authentication) — see the control section below for these in your framework.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-101820
Vulnerability Data
In Znuny through 7.3.6, an attacker can bypass specific standard login procedures and gain unauthorized access to sensitive system functions by manipulating a specific HTTP request header. Because the application incorrectly trusts this header, an attacker can impersonate any user,…
more
including administrators, without requiring a password. This grants full access to confidential data and system controls. More specifically, the HTTPBasicAuth modules for the agent (Kernel::System::Auth::HTTPBasicAuth) and customer (Kernel::System::CustomerAuth::HTTPBasicAuth) interfaces read the username to log in not only from $ENV{REMOTE_USER} (set by the web server after successful authentication), but also, as a fallback, from $ENV{HTTP_REMOTE_USER}, which is populated directly from an attacker-controllable "Remote-User" request header. On systems where HTTPBasicAuth was configured as the authentication backend, this allowed an attacker to log in as any existing user by sending a request with a forged Remote-User header, without providing any credentials.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 7 hardening rules · 4 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
Information flow enforcement can require that data or decisions are taken only from explicitly approved, higher-trust sources rather than less-verified ones.
Device identification and authentication forces verification of the source before any data it supplies is used, eliminating reliance on unauthenticated inputs.
Boundary protection monitors and filters traffic at external interfaces, structurally limiting the ability to accept data from less-trusted external sources.
Provenance tracking supplies the information needed to distinguish and prefer more-trusted sources, reducing the chance that a weaker source is chosen.
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.
Correlating multiple sources can surface discrepancies that discourage reliance on the less-trusted one.
Explicit authenticity/integrity checks before use directly reduce selection of a less-trusted source.
Protecting data-in-transit integrity helps ensure the more-trusted source is the one whose data is accepted.
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.
Network security controls can enforce trusted data paths and source validation, reducing reliance on unverified inputs.
Secure network services include source validation and integrity checks that help prevent acceptance of data from less-trusted origins.
A.8.26 requires identifying and specifying security requirements (including input validation, trust levels, and resilience against injections) but does not itself enforce, implement, or configure any mechanism that stops CWE-348 from being exploited; it is a requirements-gathering control whose effect depends on other controls (e.g. 8.24, 8.5) being correctly realized.
A.8.27 mandates security-by-design principles (distrust external input, least privilege, assume breach, defense-in-depth, secure design review against attack patterns) that reach some but not most instances of preferring a less-trustworthy source; a bounded remainder (e.g. legacy code or un-reviewed third-party components) can still introduce the flaw
Secure coding practices can enforce checks that prefer or validate the more trusted data source.
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` (higher-evidence rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- 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. blocks CWE-348
Oracle Linux 9 (1 rule)
- V-271525 OL 9 must have GPG signature verification enabled for all software repositories. blocks CWE-348
RHEL 7 (1 rule)
- 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. blocks CWE-348