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CVE-2026-39373

Status: AnalyzedMedium (5.3)—

JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by sending crafted JWE tokens with ZIP compression. The existing patch for CVE-2024-28102 limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can cause memory exhaustion on memory-constrained systems. A token under the 250KB input limit can decompress to approximately 100MB. This vulnerability is fixed in 1.5.7.

CVSS

Exploitation probability (EPSS)

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)

Latchset — Jwcrypto

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2026-39373",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
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          "id": "CVE-2026-39373",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-04-07T20:22:50.934916Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
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        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "LOW",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      }
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  "affected": [
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      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "latchset",
          "product": "jwcrypto",
          "versions": [
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              "status": "affected",
              "version": "< 1.5.7"
            }
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  "published": "2026-04-07T20:16:32.133",
  "references": [
    {
      "url": "https://github.com/latchset/jwcrypto/security/advisories/GHSA-fjrm-76x2-c4q4",
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        "Vendor Advisory"
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  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "description": [
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          "value": "CWE-409"
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      "lang": "en",
      "value": "JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by sending crafted JWE tokens with ZIP compression. The existing patch for CVE-2024-28102  limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can cause memory exhaustion on memory-constrained systems. A token under the 250KB input limit can decompress to approximately 100MB. This vulnerability is fixed in 1.5.7."
    },
    {
      "lang": "es",
      "value": "JWCrypto implementa las especificaciones JWK, JWS y JWE utilizando python-cryptography. Antes de la 1.5.7, un atacante no autenticado puede agotar la memoria del servidor enviando tokens JWE manipulados con compresión ZIP. El parche existente para CVE-2024-28102 limita el tamaño del token de entrada a 250KB, pero no valida el tamaño de la salida descomprimida. Un atacante no autenticado puede causar el agotamiento de la memoria en sistemas con recursos de memoria limitados. Un token por debajo del límite de entrada de 250KB puede descomprimirse a aproximadamente 100MB. Esta vulnerabilidad está corregida en la versión 1.5.7."
    }
  ],
  "lastModified": "2026-07-24T21:10:00.143",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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