{
  "threat_severity" : "Moderate",
  "public_date" : "2026-03-13T13:23:00Z",
  "bugzilla" : {
    "description" : "openssl: OpenSSL TLS 1.3 server may choose unexpected key agreement group",
    "id" : "2447327",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2447327"
  },
  "cvss3" : {
    "cvss3_base_score" : "6.5",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L",
    "status" : "verified"
  },
  "cwe" : "CWE-325",
  "details" : [ "Issue summary: An OpenSSL TLS 1.3 server may fail to negotiate the expected\npreferred key exchange group when its key exchange group configuration includes\nthe default by using the 'DEFAULT' keyword.\nImpact summary: A less preferred key exchange may be used even when a more\npreferred group is supported by both client and server, if the group\nwas not included among the client's initial predicated keyshares.\nThis will sometimes be the case with the new hybrid post-quantum groups,\nif the client chooses to defer their use until specifically requested by\nthe server.\nIf an OpenSSL TLS 1.3 server's configuration uses the 'DEFAULT' keyword to\ninterpolate the built-in default group list into its own configuration, perhaps\nadding or removing specific elements, then an implementation defect causes the\n'DEFAULT' list to lose its 'tuple' structure, and all server-supported groups\nwere treated as a single sufficiently secure 'tuple', with the server not\nsending a Hello Retry Request (HRR) even when a group in a more preferred tuple\nwas mutually supported.\nAs a result, the client and server might fail to negotiate a mutually supported\npost-quantum key agreement group, such as 'X25519MLKEM768', if the client's\nconfiguration results in only 'classical' groups (such as 'X25519' being the\nonly ones in the client's initial keyshare prediction).\nOpenSSL 3.5 and later support a new syntax for selecting the most preferred TLS\n1.3 key agreement group on TLS servers.  The old syntax had a single 'flat'\nlist of groups, and treated all the supported groups as sufficiently secure.\nIf any of the keyshares predicted by the client were supported by the server\nthe most preferred among these was selected, even if other groups supported by\nthe client, but not included in the list of predicted keyshares would have been\nmore preferred, if included.\nThe new syntax partitions the groups into distinct 'tuples' of roughly\nequivalent security.  Within each tuple the most preferred group included among\nthe client's predicted keyshares is chosen, but if the client supports a group\nfrom a more preferred tuple, but did not predict any corresponding keyshares,\nthe server will ask the client to retry the ClientHello (by issuing a Hello\nRetry Request or HRR) with the most preferred mutually supported group.\nThe above works as expected when the server's configuration uses the built-in\ndefault group list, or explicitly defines its own list by directly defining the\nvarious desired groups and group 'tuples'.\nNo OpenSSL FIPS modules are affected by this issue, the code in question lies\noutside the FIPS boundary.\nOpenSSL 3.6 and 3.5 are vulnerable to this issue.\nOpenSSL 3.6 users should upgrade to OpenSSL 3.6.2 once it is released.\nOpenSSL 3.5 users should upgrade to OpenSSL 3.5.6 once it is released.\nOpenSSL 3.4, 3.3, 3.0, 1.0.2 and 1.1.1 are not affected by this issue.", "A key group selection preference flaw has been discovered in OpenSSL. An OpenSSL TLS 1.3 server may fail to negotiate the expected preferred key exchange group when its key exchange group configuration includes the default by using the \"DEFAULT\" keyword. A less preferred key exchange may be used even when a more preferred group is supported by both client and server, if the group was not included among the client's initial predicated keyshares. This will sometimes be the case with the new hybrid post-quantum groups, if the client chooses to defer their use until specifically requested by the server. No OpenSSL FIPS modules are affected by this issue, the code in question lies outside the FIPS boundary." ],
  "statement" : "The impact of this flaw is limited to the choice of key agreement groups in a specific TLS connection. While a less a preferred key agreement group may allow for a connection to lack post-quantum protection, it is important to know that the connection will still be encrypted with a secure classical cipher and that the degradation of the cipher is limited to the active connection and is not a persistent degradation. Groups which the server operator has disallowed will not be used and it may be the case that the client and server fail to agree upon a key exchange group which would prevent the offending client from constructing a TLS connection.",
  "affected_release" : [ {
    "product_name" : "Red Hat JBoss Core Services 2.4.62.SP4",
    "release_date" : "2026-06-22T00:00:00Z",
    "advisory" : "RHSA-2026:27201",
    "cpe" : "cpe:/a:redhat:jboss_core_services:1",
    "package" : "jbcs-httpd24-openssl"
  }, {
    "product_name" : "Red Hat Hardened Images",
    "release_date" : "2026-04-09T00:00:00Z",
    "advisory" : "RHSA-2026:7261",
    "cpe" : "cpe:/a:redhat:hummingbird:1",
    "package" : "openssl-main-3.5.6-0.1.hum1"
  } ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Will not fix",
    "package_name" : "openssl",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Not affected",
    "package_name" : "openssl-fips-provider",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "openssl",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "openssl098e",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "openssl",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "openssl098e",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "compat-openssl10",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "mingw-openssl",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "openssl",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Not affected",
    "package_name" : "compat-openssl11",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Will not fix",
    "package_name" : "openssl",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "openssl-fips-provider",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-2673\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-2673\nhttps://github.com/openssl/openssl/commit/2157c9d81f7b0bd7dfa25b960e928ec28e8dd63f\nhttps://github.com/openssl/openssl/commit/85977e013f32ceb96aa034c0e741adddc1a05e34\nhttps://openssl-library.org/news/secadv/20260313.txt" ],
  "name" : "CVE-2026-2673",
  "mitigation" : {
    "value" : "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.",
    "lang" : "en:us"
  },
  "csaw" : false
}