CVE-2026-77696 (GCVE-0-2026-77696)

Vulnerability from cvelistv5 – Published: 2026-09-29 15:32 – Updated: 2026-11-10 12:49
VLAI
Title
Timing Side-Channel in SM2 Signature Generation
Summary
Issue summary: SM2 signature generation uses non-constant-time arithmetic on secret values, forming a timing side-channel. Impact summary: An attacker able to measure SM2 signing times may learn information about the per-signature secret nonce, which over many signatures can, via a lattice / Hidden Number Problem attack, lead to recovery of the private key. CWE: CWE-208: Observable Timing Discrepancy Description: SM2 signature generation computes the signature value using variable-time BIGNUM operations on the secret nonce and the private key, so the time taken to produce an SM2 signature depends on these secret values, forming a timing side-channel. Applications performing SM2 signature generation are affected on all platforms. FIPS Impact: no SM2 is not a FIPS algorithm.
Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-29 16:51 UTC
CWE
  • CWE-208 - Observable Timing Discrepancy
Assigner
openssl CNA under the mitre root
CNA scorecard B 78/100 over 48 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
OpenSSL OpenSSL Affected: 4.0.0 , < 4.0.3 (semver)
Affected: 3.6.0 , < 3.6.5 (semver)
Affected: 3.5.0 , < 3.5.9 (semver)
Affected: 3.4.0 , < 3.4.8 (semver)
Affected: 3.0.0 , < 3.0.23 (semver)
Affected: 1.1.1 , < 1.1.1zj (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) Affected: V3.1.7 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) Affected: V3.1.7 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) Affected: V3.1.7 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) Affected: V3.1.7 , < * (custom)
guessed Create a notification for this product.
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) Affected: V3.1.7 , < * (custom)
guessed Create a notification for this product.
Date Public
2026-09-29 14:21
Credits
Vladimir Tokarev Igor Ustinov Viktor Dukhovni
Show details on NVD website
To clipboard 

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      "status": "final",
      "title": "openssl: OpenSSL: Private key recovery via SM2 timing side-channel",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-77696.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-11-12T01:18:57Z",
      "cve": "CVE-2026-77696",
      "id": "CVE-2026-77696",
      "initial_release_date": "2026-10-02T16:48:50Z",
      "product_status:known_affected": "537",
      "product_status:known_not_affected": "265",
      "product_status:recommended": "202",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-77696",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-77696.json",
      "version": "14"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "affected": [
              {
                "defaultStatus": "unknown",
                "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)",
                "vendor": "Siemens",
                "versions": [
                  {
                    "lessThan": "*",
                    "status": "affected",
                    "version": "V3.1.7",
                    "versionType": "custom"
                  }
                ]
              },
              {
                "defaultStatus": "unknown",
                "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)",
                "vendor": "Siemens",
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                    "version": "V3.1.7",
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                  }
                ]
              },
              {
                "defaultStatus": "unknown",
                "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)",
                "vendor": "Siemens",
                "versions": [
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                    "status": "affected",
                    "version": "V3.1.7",
                    "versionType": "custom"
                  }
                ]
              },
              {
                "defaultStatus": "unknown",
                "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)",
                "vendor": "Siemens",
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                  {
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                    "status": "affected",
                    "version": "V3.1.7",
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                ]
              },
              {
                "defaultStatus": "unknown",
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                "vendor": "Siemens",
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                    "lessThan": "*",
                    "status": "affected",
                    "version": "V3.1.7",
                    "versionType": "custom"
                  }
                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-11-10T12:49:50.567Z",
              "orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
              "shortName": "siemens-SADP"
            },
            "references": [
              {
                "url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html"
              }
            ],
            "x_adpType": "supplier"
          },
          {
            "metrics": [
              {
                "cvssV3_1": {
                  "attackComplexity": "HIGH",
                  "attackVector": "NETWORK",
                  "availabilityImpact": "NONE",
                  "baseScore": 3.7,
                  "baseSeverity": "LOW",
                  "confidentialityImpact": "LOW",
                  "integrityImpact": "NONE",
                  "privilegesRequired": "NONE",
                  "scope": "UNCHANGED",
                  "userInteraction": "NONE",
                  "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
                  "version": "3.1"
                }
              },
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-77696",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-09-29T16:51:30.070097Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-09-29T16:51:26.361Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "OpenSSL",
              "vendor": "OpenSSL",
              "versions": [
                {
                  "lessThan": "4.0.3",
                  "status": "affected",
                  "version": "4.0.0",
                  "versionType": "semver"
                },
                {
                  "lessThan": "3.6.5",
                  "status": "affected",
                  "version": "3.6.0",
                  "versionType": "semver"
                },
                {
                  "lessThan": "3.5.9",
                  "status": "affected",
                  "version": "3.5.0",
                  "versionType": "semver"
                },
                {
                  "lessThan": "3.4.8",
                  "status": "affected",
                  "version": "3.4.0",
                  "versionType": "semver"
                },
                {
                  "lessThan": "3.0.23",
                  "status": "affected",
                  "version": "3.0.0",
                  "versionType": "semver"
                },
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                  "lessThan": "1.1.1zj",
                  "status": "affected",
                  "version": "1.1.1",
                  "versionType": "custom"
                }
              ]
            }
          ],
          "credits": [
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              "lang": "en",
              "type": "reporter",
              "value": "Vladimir Tokarev"
            },
            {
              "lang": "en",
              "type": "remediation developer",
              "value": "Igor Ustinov"
            },
            {
              "lang": "en",
              "type": "remediation developer",
              "value": "Viktor Dukhovni"
            }
          ],
          "datePublic": "2026-09-29T14:21:57.000Z",
          "descriptions": [
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              "lang": "en",
              "supportingMedia": [
                {
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                  "type": "text/html",
                  "value": "Issue summary: SM2 signature generation uses non-constant-time arithmetic\u003cbr\u003eon secret values, forming a timing side-channel.\u003cbr\u003e\u003cbr\u003eImpact summary: An attacker able to measure SM2 signing times may learn\u003cbr\u003einformation about the per-signature secret nonce, which over many signatures\u003cbr\u003ecan, via a lattice / Hidden Number Problem attack, lead to recovery of the\u003cbr\u003eprivate key.\u003cbr\u003e\u003cbr\u003eCWE: CWE-208: Observable Timing Discrepancy\u003cbr\u003e\u003cbr\u003eDescription: SM2 signature generation computes the signature value using\u003cbr\u003evariable-time BIGNUM operations on the secret nonce and the private key, so\u003cbr\u003ethe time taken to produce an SM2 signature depends on these secret values,\u003cbr\u003eforming a timing side-channel.\u003cbr\u003e\u003cbr\u003eApplications performing SM2 signature generation are affected on all\u003cbr\u003eplatforms.\u003cbr\u003e\u003cbr\u003eFIPS Impact: no\u003cbr\u003eSM2 is not a FIPS algorithm."
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              ],
              "value": "Issue summary: SM2 signature generation uses non-constant-time arithmetic\non secret values, forming a timing side-channel.\n\nImpact summary: An attacker able to measure SM2 signing times may learn\ninformation about the per-signature secret nonce, which over many signatures\ncan, via a lattice / Hidden Number Problem attack, lead to recovery of the\nprivate key.\n\nCWE: CWE-208: Observable Timing Discrepancy\n\nDescription: SM2 signature generation computes the signature value using\nvariable-time BIGNUM operations on the secret nonce and the private key, so\nthe time taken to produce an SM2 signature depends on these secret values,\nforming a timing side-channel.\n\nApplications performing SM2 signature generation are affected on all\nplatforms.\n\nFIPS Impact: no\nSM2 is not a FIPS algorithm."
            }
          ],
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            {
              "format": "other",
              "other": {
                "content": {
                  "text": "Low"
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                "type": "https://openssl-library.org/policies/general/security-policy/"
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            "orgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5",
            "shortName": "openssl"
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          "references": [
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              "name": "OpenSSL Advisory",
              "tags": [
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              "url": "https://openssl-library.org/news/secadv/20260929.txt"
            },
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              "name": "4.0.3 git commit",
              "tags": [
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              ],
              "url": "https://github.com/openssl/openssl/commit/20b20628d39b2dcc4677194bd68c7c060fa598cb"
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            {
              "name": "3.6.5 git commit",
              "tags": [
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              ],
              "url": "https://github.com/openssl/openssl/commit/1c4aed808a7aea32d2d013049c2e0d9fef164fc9"
            },
            {
              "name": "3.5.9 git commit",
              "tags": [
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              ],
              "url": "https://github.com/openssl/openssl/commit/6b90445a56b99a328ac1feba058abf976504f440"
            },
            {
              "name": "3.4.8 git commit",
              "tags": [
                "patch"
              ],
              "url": "https://github.com/openssl/openssl/commit/419f5cb519721dceed393dbc524d79e487c72e64"
            }
          ],
          "source": {
            "discovery": "UNKNOWN"
          },
          "title": "Timing Side-Channel in SM2 Signature Generation",
          "x_generator": {
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          }
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      },
      "cveMetadata": {
        "assignerOrgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5",
        "assignerShortName": "openssl",
        "cveId": "CVE-2026-77696",
        "datePublished": "2026-09-29T15:32:22.520Z",
        "dateReserved": "2026-08-21T07:47:36.032Z",
        "dateUpdated": "2026-11-10T12:49:50.567Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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Vulnerability timeline

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