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: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:X/R:X/V:X/RE:X/U:XSummary
CVE-2026-27804 is a critical-severity Use of a Broken or Risky Cryptographic Algorithm (CWE-327) vulnerability in Parseplatform Parse-Server. Its CVSS base score is 9.3 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Mark-of-the-Web Bypass (T1553.005); ranked at the 7th 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-13 (Cryptographic Protection) and SC-23 (Session Authenticity) — 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-2026-27804 is a critical vulnerability in Parse Server, an open source backend deployable on any Node.js infrastructure. In versions prior to 8.6.3 and 9.1.1-alpha.4, the Google authentication mechanism fails to properly validate JWT algorithms, allowing an unauthenticated attacker to forge a Google authentication token by setting the `alg` parameter to `"none"`. This flaw affects all deployments with Google authentication enabled, stemming from CWE-327 (Broken or Risky Cryptographic Algorithm) and CWE-345 (Insufficient Verification of Data Authenticity), with a CVSS v3.1 base score of 9.1.
An unauthenticated attacker can exploit this remotely over the network with low complexity and no privileges or user interaction required. By crafting a malicious JWT token claiming Google origin but using the none algorithm, the attacker can impersonate any user linked to a Google account without knowing their credentials, gaining unauthorized access to that user's data and actions within the Parse Server application.
Mitigation requires upgrading to Parse Server versions 8.6.3 or 9.1.1-alpha.4, which enforce the `RS256` algorithm instead of trusting the JWT header and replace the custom Google key fetcher with the `jwks-rsa` library that rejects unknown key IDs. As a temporary workaround, disable Google authentication until patching is feasible. Relevant details are documented in the Parse Server security advisory (GHSA-4q3h-vp4r-prv2) and release notes for the fixed versions.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8774
Vulnerability Data
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.3 and 9.1.1-alpha.4, an unauthenticated attacker can forge a Google authentication token with `alg: "none"` to log in as…
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any user linked to a Google account, without knowing their credentials. All deployments with Google authentication enabled are affected. The fix in versions 8.6.3 and 9.1.1-alpha.4 hardcodes the expected `RS256` algorithm instead of trusting the JWT header, and replaces the Google adapter's custom key fetcher with `jwks-rsa` which rejects unknown key IDs. As a workaround, dsable Google authentication until upgrading is possible.
- 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 · 10 OS baselines
V3.5.5
Mitigating Controls (NIST 800-53 r5) AI
SC-13 requires selection and implementation of specific cryptography types, directly stopping use of broken algorithms.
Explicit requirement to protect session authenticity structurally prevents the weakness for communications.
Integrity verification tools detect (but do not stop) the acceptance of data lacking authenticity.
Associating security attributes with exchanged information supports verification of authenticity.
Integrity protection on transmitted data directly stops acceptance of unauthenticated or altered 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.
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.
PR.DS-01 promotes encryption for data-at-rest but never requires strong algorithms, leaving CWE-327 fully possible; the weakness is also far broader than data-at-rest so one narrow control removes none of its total risk.
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.
Mandating approved algorithms, cipher strength and usage standards directly stops the selection of broken or weak cryptographic primitives that attackers can exploit.
Security testing can detect missing or weak data authenticity verification.
The explicit call-out of cryptography-related legal constraints (import/export, key escrow, digital-signature validity) reduces the likelihood that an organization will adopt broken or non-compliant cryptographic algorithms that violate those rules.
Access to current specialist guidance and early vulnerability alerts enables timely replacement of broken or risky cryptographic algorithms with stronger alternatives.
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.
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 (3 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-327
- 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
Windows 10 (1 rule)
- V-220937 The system must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327
Windows 11 (1 rule)
- V-253461 The system must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327
Windows Server 2016 (1 rule)
- V-225053 Windows Server 2016 must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327
Windows Server 2019 (1 rule)
- V-205654 Windows Server 2019 must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327
Windows Server 2022 (1 rule)
- V-254474 Windows Server 2022 must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327