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CVE-2021-37606

Status: ModifiedMedium (5.3)—
Severity5.3Medium · CVSS 3.1
Exploitation probability0.74 %higher than 54% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitNot knownno public code found

Meow hash 0.5/calico does not sufficiently thwart key recovery by an attacker who can query whether there's a collision in the bottom bits of the hashes of two messages, as demonstrated by an attack against a long-running web service that allows the attacker to infer collisions by measuring timing differences.

CVSS

Base score
5.3
Version
3.1
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
0.74 %
Percentile among all scored CVEs
54
Score date
10/24/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

Meow Hash Project — Meow Hash

CWEs

References

Show 4 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2021-37606",
  "cveTags": [],
  "metrics": {
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        "source": "nvd@nist.gov",
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          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:N/A:N",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
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        "acInsufInfo": false,
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        "obtainUserPrivilege": false,
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    "cvssMetricV31": [
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        "cvssData": {
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          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
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          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
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      "affectedData": [
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  "published": "2021-07-30T14:15:22.153",
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      "url": "https://news.ycombinator.com/item?id=27978878",
      "tags": [
        "Third Party Advisory"
      ],
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    {
      "url": "https://peter.website/meow-hash-cryptanalysis",
      "tags": [
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    {
      "url": "https://peter.website/meow-hash-cryptanalysis",
      "tags": [
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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  "vulnStatus": "Modified",
  "weaknesses": [
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      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-203"
        },
        {
          "lang": "en",
          "value": "CWE-326"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Meow hash 0.5/calico does not sufficiently thwart key recovery by an attacker who can query whether there's a collision in the bottom bits of the hashes of two messages, as demonstrated by an attack against a long-running web service that allows the attacker to infer collisions by measuring timing differences."
    },
    {
      "lang": "es",
      "value": "Meow hash versión 0.5/calico, no frustra suficientemente la recuperación de claves por un atacante que puede consultar si se presenta una colisión en los bits inferiores de los hashes de dos mensajes, como se ha demostrado por un ataque contra un servicio web de larga duración que permite al atacante inferir colisiones al medir las diferencias de tiempo"
    }
  ],
  "lastModified": "2026-06-17T04:00:49.443",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:meow_hash_project:meow_hash:0.5:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "5F0AAF9A-2F56-400E-B92A-C15CBA7184AD"
            }
          ],
          "operator": "OR"
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  "sourceIdentifier": "cve@mitre.org"
}