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4 vulnerabilities by refraction-networking
CVE-2026-27017 (GCVE-0-2026-27017)
Vulnerability from nvd – Published: 2026-02-20 02:47 – Updated: 2026-02-20 15:20
VLAI
Title
uTLS has a Chrome Parrot Fingerprint Vulnerability due to GREASE ECH Cipher Suite Mismatch
Summary
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 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.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
- CWE-1240 - Use of a Cryptographic Primitive with a Risky Implementation
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://github.com/refraction-networking/utls/sec… | x_refsource_CONFIRM |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| refraction-networking | utls |
Affected:
>= 1.6.0, < 1.8.1
|
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CVE-2026-26994 (GCVE-0-2026-26994)
Vulnerability from nvd – Published: 2026-02-20 02:50 – Updated: 2026-02-20 15:12
VLAI
Title
uTLS ServerHellos are accepted without checking TLS 1.3 downgrade canaries
Summary
uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. In versions 1.6.7 and below, uTLS did not implement the TLS 1.3 downgrade protection mechanism specified in RFC 8446 Section 4.1.3 when using a uTLS ClientHello spec. This allowed an active network adversary to downgrade TLS 1.3 connections initiated by a uTLS client to a lower TLS version (e.g., TLS 1.2) by modifying the ClientHello message to exclude the SupportedVersions extension, causing the server to respond with a TLS 1.2 ServerHello (along with a downgrade canary in the ServerHello random field). Because uTLS did not check the downgrade canary in the ServerHello random field, clients would accept the downgraded connection without detecting the attack. This attack could also be used by an active network attacker to fingerprint uTLS connections. This issue has been fixed in version 1.7.0.
Severity
6.5 (Medium)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
- CWE-693 - Protection Mechanism Failure
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/refraction-networking/utls/sec… | x_refsource_CONFIRM |
| https://github.com/refraction-networking/utls/iss… | x_refsource_MISC |
| https://github.com/refraction-networking/utls/pull/337 | x_refsource_MISC |
| https://github.com/refraction-networking/utls/com… | x_refsource_MISC |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| refraction-networking | utls |
Affected:
< 1.7.0
|
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CVE-2026-26994 (GCVE-0-2026-26994)
Vulnerability from cvelistv5 – Published: 2026-02-20 02:50 – Updated: 2026-02-20 15:12
VLAI
Title
uTLS ServerHellos are accepted without checking TLS 1.3 downgrade canaries
Summary
uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. In versions 1.6.7 and below, uTLS did not implement the TLS 1.3 downgrade protection mechanism specified in RFC 8446 Section 4.1.3 when using a uTLS ClientHello spec. This allowed an active network adversary to downgrade TLS 1.3 connections initiated by a uTLS client to a lower TLS version (e.g., TLS 1.2) by modifying the ClientHello message to exclude the SupportedVersions extension, causing the server to respond with a TLS 1.2 ServerHello (along with a downgrade canary in the ServerHello random field). Because uTLS did not check the downgrade canary in the ServerHello random field, clients would accept the downgraded connection without detecting the attack. This attack could also be used by an active network attacker to fingerprint uTLS connections. This issue has been fixed in version 1.7.0.
Severity
6.5 (Medium)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
- CWE-693 - Protection Mechanism Failure
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/refraction-networking/utls/sec… | x_refsource_CONFIRM |
| https://github.com/refraction-networking/utls/iss… | x_refsource_MISC |
| https://github.com/refraction-networking/utls/pull/337 | x_refsource_MISC |
| https://github.com/refraction-networking/utls/com… | x_refsource_MISC |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| refraction-networking | utls |
Affected:
< 1.7.0
|
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CVE-2026-27017 (GCVE-0-2026-27017)
Vulnerability from cvelistv5 – Published: 2026-02-20 02:47 – Updated: 2026-02-20 15:20
VLAI
Title
uTLS has a Chrome Parrot Fingerprint Vulnerability due to GREASE ECH Cipher Suite Mismatch
Summary
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 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.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
- CWE-1240 - Use of a Cryptographic Primitive with a Risky Implementation
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://github.com/refraction-networking/utls/sec… | x_refsource_CONFIRM |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| refraction-networking | utls |
Affected:
>= 1.6.0, < 1.8.1
|
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"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}