{"id":"GHSA-7m29-f4hw-g2vx","revision":null,"records":[{"revision":"f3a3cfc1045e432abf87ab27e1a6a5b9","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-27017","aliases":[],"title":"uTLS has a Chrome Parrot Fingerprint Vulnerability due to GREASE ECH Cipher Suite Mismatch","description":"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.","state":0,"publishedAt":"2026-02-20T02:47:17.899+00:00","modifiedAt":"2026-02-20T15:20:18.976+00:00","affected":[{"ecosystem":"Vendor product","name":"utls","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"refraction-networking\",\n                    \"product\": \"utls\",\n                    \"versions\": [\n                        {\n                            \"version\": \">= 1.6.0, < 1.8.1\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","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","score":2.3,"severity":"LOW"}],"references":["https://github.com/refraction-networking/utls/security/advisories/GHSA-7m29-f4hw-g2vx"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-27017","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-27017","identifiers":["CVE-2026-27017"]},"retained":false,"historicalAffected":[]},{"revision":"50e7ec991ec84ad6a7ff173e8ae3fd36","observedAt":"2026-11-15T08:36:03.681+00:00","statement":{"source":"euvd","id":"EUVD-2026-8031","aliases":["CVE-2026-27017","GHSA-7m29-f4hw-g2vx"],"title":"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 c…","description":"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.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 4.0","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","score":2.3,"severity":null}],"references":["https://github.com/refraction-networking/utls/security/advisories/GHSA-7m29-f4hw-g2vx"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-8031","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Feb 20, 2026, 2:47:17 AM","dateUpdated":"Feb 20, 2026, 3:20:18 PM"},"relatedAdvisories":[{"id":"openSUSE-SU-2026:21653-1","title":"Security update for v2ray-core","vulnerabilityIds":["CVE-2026-27017","CVE-2026-39821","CVE-2026-72815","CVE-2026-72816","CVE-2026-72817"]},{"id":"openSUSE-SU-2026:10913-1","title":"golang-github-v2fly-v2ray-core-5.51.2-1.1 on GA media","vulnerabilityIds":["CVE-2026-27017","CVE-2026-39821"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-8031","identifiers":["EUVD-2026-8031","CVE-2026-27017","GHSA-7m29-f4hw-g2vx"]},"retained":false,"historicalAffected":[]},{"revision":"867b778952da415cbe21084527a2756c","observedAt":"2026-10-25T06:17:28.833+00:00","statement":{"source":"nvd","id":"CVE-2026-27017","aliases":[],"title":"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 c…","description":"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. 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Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-27017","identifiers":["CVE-2026-27017"]},"retained":false,"historicalAffected":[]},{"revision":"841b95858b044a6199cb410930229f67","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-7m29-f4hw-g2vx","aliases":["CVE-2026-27017","GO-2026-4509"],"title":"uTLS has a fingerprint vulnerability from GREASE ECH mismatch for Chrome parrots","description":"There is a fingerprint mismatch with Chrome when using GREASE ECH, having to do with ciphersuite selection. When Chrome selects the preferred ciphersuite in the outer ClientHello and the ciphersuite for ECH, it does so consistently based on hardware support. That means, for example, if it prefers AES for the outer ciphersuite, it would also use AES for ECH. The Chrome parrot in utls hardcodes AES preference for outer ciphersuites but selects the ECH ciphersuite randomly between AES and ChaCha20. So there is a 50% chance of selecting ChaCha20 for ECH while using AES for the outer ciphersuite, which is impossible in Chrome.\n\nThis is only a problem in GREASE ECH, since in real ECH Chrome selects the first valid ciphersuite when AES is preferred, which is the same in utls. So no change is done there.\n\nAffected symbols: `HelloChrome_120`, `HelloChrome_120_PQ`, `HelloChrome_131`, `HelloChrome_133`\n\nFix commit: 24bd1e05a788c1add7f3037f4532ea552b2cee07\n\nThanks to telegram @acgdaily for reporting this issue.","state":0,"publishedAt":"2026-02-18T22:33:18+00:00","modifiedAt":"2026-09-10T03:50:34.3155519+00:00","affected":[{"ecosystem":"Go","name":"github.com/refraction-networking/utls","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"1.6.0"},{"kind":"fixed","version":"1.8.1"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V4","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","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"LOW"}],"references":["https://github.com/refraction-networking/utls/security/advisories/GHSA-7m29-f4hw-g2vx","https://nvd.nist.gov/vuln/detail/CVE-2026-27017","https://github.com/refraction-networking/utls/commit/24bd1e05a788c1add7f3037f4532ea552b2cee07","https://github.com/refraction-networking/utls","https://github.com/refraction-networking/utls/releases/tag/v1.8.1","https://pkg.go.dev/vuln/GO-2026-4509"],"sourceUrl":"https://github.com/advisories/GHSA-7m29-f4hw-g2vx","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-7m29-f4hw-g2vx","identifiers":["GHSA-7m29-f4hw-g2vx","CVE-2026-27017","GO-2026-4509"]},"retained":false,"historicalAffected":[]},{"revision":"dbe5addee505486788e522a8b8b84f7a","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GO-2026-4509","aliases":["CVE-2026-27017","GHSA-7m29-f4hw-g2vx"],"title":"Fingerprint vulnerability in uTLS from GREASE ECH mismatch for Chrome parrots in github.com/refraction-networking/utls","description":"Fingerprint vulnerability in uTLS from GREASE ECH mismatch for Chrome parrots in github.com/refraction-networking/utls","state":0,"publishedAt":"2026-02-24T23:10:26+00:00","modifiedAt":"2026-02-24T23:41:14.415506+00:00","affected":[{"ecosystem":"Go","name":"github.com/refraction-networking/utls","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"1.6.0"},{"kind":"fixed","version":"1.8.1"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://github.com/refraction-networking/utls/security/advisories/GHSA-7m29-f4hw-g2vx","https://github.com/refraction-networking/utls/commit/24bd1e05a788c1add7f3037f4532ea552b2cee07","https://github.com/refraction-networking/utls/releases/tag/v1.8.1"],"sourceUrl":"https://osv.dev/vulnerability/GO-2026-4509","license":"OSV · upstream source license applies","key":"osv:GO-2026-4509","identifiers":["GO-2026-4509","CVE-2026-27017","GHSA-7m29-f4hw-g2vx"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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