CVE-2026-27017
Refraction-Networking Utls 1.6.0 – 1.8.1
Raw vector
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:L/VI:N/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-2026-27017 is a low-severity Use of a Cryptographic Primitive with a Risky Implementation (CWE-1240) vulnerability in Refraction-Networking Utls. Its CVSS base score is 2.3 (Low).
Operationally, exploitation aligns with the MITRE ATT&CK technique Weaken Encryption (T1600); ranked at the 5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8031
Vulnerability Data
uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. Versions 1.6.0 through 1.8.0 contain a fingerprint mismatch with Chrome when using GREASE ECH, related to cipher suite selection. When…
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Chrome selects the preferred cipher suite in the outer ClientHello and for ECH, it does so consistently based on hardware support—for example, if it prefers AES for the outer cipher suite, it also uses AES for ECH. However, the Chrome parrot in uTLS hardcodes AES preference for outer cipher suites but selects the ECH cipher suite randomly between AES and ChaCha20. This creates a 50% chance of selecting ChaCha20 for ECH while using AES for the outer cipher suite, a combination impossible in Chrome. This issue only affects GREASE ECH; in real ECH, Chrome selects the first valid cipher suite when AES is preferred, which uTLS handles correctly. This issue has been fixed in version 1.8.1.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 12 hardening rules · 3 OS baselines
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Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Requires specific, validated cryptographic primitives, reducing use of risky or improperly implemented primitives.
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 require use of approved, proven cryptographic implementations and forbid risky custom ones.
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.
Mandates approved cryptographic controls, directly preventing use of risky or non-compliant implementations.
Security testing can detect use of weak or non-compliant cryptographic primitives before deployment.
Secure SDLC requires vetted crypto libraries and standards, reducing risky custom implementations.
Application security requirements can specify approved cryptographic standards and disallow risky primitives.
Secure architecture principles include selection of proven cryptographic components and avoidance of custom risky implementations.
Secure coding standards prohibit non-standard or disallowed cryptographic algorithms.
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-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-1240
- V-248534 OL 8 must employ FIPS 140-2 approved cryptographic hashing algorithms for all stored passwords. prevents CWE-1240
Oracle Linux 9 (1 rule)
- V-271628 OL 9 must employ FIPS 140-3 approved cryptographic hashing algorithms for all stored passwords. prevents CWE-1240
RHEL 8 (2 rules)
- V-230223 RHEL 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-1240
- V-230224 All RHEL 8 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at rest protection. prevents CWE-1240