Schannel cipher selection surprise

{
  "id": "1d8184996c7d019ccc5ba4fc82619fb3f723512380fbdbbecde4624727aeff86",
  "url": "https://osv.dev/vulnerability/CURL-CVE-2021-22897",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Schannel cipher selection surprise",
    "summary": "libcurl lets applications specify which specific TLS ciphers to use in transfers, using the option called `CURLOPT_SSL_CIPHER_LIST`. The cipher selection is used for the TLS negotiation when a transfer is done involving any of the TLS based transfer protocols libcurl supports, such as HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. Due to a mistake in the code, the selected cipher set was stored in a single \"static\" variable in the library, which has the surprising side-effect that if an application sets up multiple concurrent transfers, the last one that sets the ciphers accidentally controls the set used by all transfers. In a worst-case scenario, this weakens transport security significantly.",
    "evidence": "osv:CURL-CVE-2021-22897",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CURL-CVE-2021-22897",
      "aliases": [
        "CURL-CVE-2021-22897",
        "CVE-2021-22897"
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "7.61.0"
                },
                {
                  "fixed": "7.77.0"
                }
              ]
            },
            {
              "repo": "https://github.com/curl/curl.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "9aefbff30d280c60fc9d8cc3e0b2f19fc70a2f28"
                },
                {
                  "fixed": "bbb71507b7bab52002f9b1e0880bed6a32834511"
                }
              ]
            }
          ],
          "versions": [
            "7.76.1",
            "7.76.0",
            "7.75.0",
            "7.74.0",
            "7.73.0",
            "7.72.0",
            "7.71.1",
            "7.71.0",
            "7.70.0",
            "7.69.1",
            "7.69.0",
            "7.68.0",
            "7.67.0",
            "7.66.0",
            "7.65.3",
            "7.65.2",
            "7.65.1",
            "7.65.0",
            "7.64.1",
            "7.64.0",
            "7.63.0",
            "7.62.0",
            "7.61.1",
            "7.61.0",
            "curl-7_76_1",
            "curl-7_76_0",
            "curl-7_75_0",
            "curl-7_74_0",
            "curl-7_73_0",
            "tiny-curl-7_72_0",
            "curl-7_72_0",
            "curl-7_71_1",
            "curl-7_71_0",
            "curl-7_70_0",
            "curl-7_69_1",
            "curl-7_69_0",
            "curl-7_68_0",
            "curl-7_67_0",
            "curl-7_66_0",
            "curl-7_65_3",
            "curl-7_65_2",
            "curl-7_65_1",
            "curl-7_65_0",
            "curl-7_64_1",
            "curl-7_64_0",
            "curl-7_63_0",
            "curl-7_62_0",
            "curl-7_61_1",
            "curl-7_61_0"
          ],
          "database_specific": {
            "source": "https://curl.se/docs/CURL-CVE-2021-22897.json",
            "vanir_signatures": [
              {
                "id": "CURL-CVE-2021-22897-369c7e73",
                "digest": {
                  "threshold": 0.9,
                  "line_hashes": [
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                },
                "source": "https://github.com/curl/curl.git/commit/bbb71507b7bab52002f9b1e0880bed6a32834511",
                "target": {
                  "file": "lib/vtls/schannel.c"
                },
                "deprecated": false,
                "signature_type": "Line",
                "signature_version": "v1"
              },
              {
                "id": "CURL-CVE-2021-22897-731f3de3",
                "digest": {
                  "threshold": 0.9,
                  "line_hashes": [
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                },
                "source": "https://github.com/curl/curl.git/commit/bbb71507b7bab52002f9b1e0880bed6a32834511",
                "target": {
                  "file": "lib/vtls/schannel.h"
                },
                "deprecated": false,
                "signature_type": "Line",
                "signature_version": "v1"
              },
              {
                "id": "CURL-CVE-2021-22897-a0ff66c6",
                "digest": {
                  "length": 14322,
                  "function_hash": "211186878913764398743821657885986770610"
                },
                "source": "https://github.com/curl/curl.git/commit/bbb71507b7bab52002f9b1e0880bed6a32834511",
                "target": {
                  "file": "lib/vtls/schannel.c",
                  "function": "schannel_connect_step1"
                },
                "deprecated": false,
                "signature_type": "Function",
                "signature_version": "v1"
              },
              {
                "id": "CURL-CVE-2021-22897-f33500b8",
                "digest": {
                  "length": 676,
                  "function_hash": "36431407875438539121636832984401189544"
                },
                "source": "https://github.com/curl/curl.git/commit/bbb71507b7bab52002f9b1e0880bed6a32834511",
                "target": {
                  "file": "lib/vtls/schannel.c",
                  "function": "set_ssl_ciphers"
                },
                "deprecated": false,
                "signature_type": "Function",
                "signature_version": "v1"
              }
            ],
            "vanir_signatures_modified": "2026-10-25T01:04:45Z"
          }
        }
      ],
      "modified": "2026-10-25T01:04:45.728326687Z",
      "provider": "osv",
      "references": [],
      "provider_metadata": {
        "CWE": {
          "id": "CWE-488",
          "desc": "Exposure of Data Element to Wrong Session"
        },
        "URL": "https://curl.se/docs/CVE-2021-22897.json",
        "www": "https://curl.se/docs/CVE-2021-22897.html",
        "award": {
          "amount": "800",
          "currency": "USD"
        },
        "issue": "https://hackerone.com/reports/1172857",
        "affects": "both",
        "package": "curl",
        "severity": "Low",
        "last_affected": "7.76.1"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2021-22897",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 444286,
  "published_at": "2021-05-26T08:00:00+00:00"
}