CVE-2026-48523 (GCVE-0-2026-48523)

Vulnerability from cvelistv5 – Published: 2026-05-28 15:10 – Updated: 2026-05-28 15:27
VLAI
Title
PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys
Summary
PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.
Severity
5.4 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
SSVC
Exploitation: poc Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-347 - Improper Verification of Cryptographic Signature
Assigner
References
Impacted products
Vendor Product Version
jpadilla pyjwt Affected: >= 2.9.0, < 2.13.0
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-48523",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-28T15:27:44.771049Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-28T15:27:49.780Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "pyjwt",
          "vendor": "jpadilla",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.9.0, \u003c 2.13.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.4,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-347",
              "description": "CWE-347: Improper Verification of Cryptographic Signature",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-28T15:10:19.141Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f"
        }
      ],
      "source": {
        "advisory": "GHSA-jq35-7prp-9v3f",
        "discovery": "UNKNOWN"
      },
      "title": "PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-48523",
    "datePublished": "2026-05-28T15:10:19.141Z",
    "dateReserved": "2026-05-21T16:18:10.619Z",
    "dateUpdated": "2026-05-28T15:27:49.780Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-48523",
      "date": "2026-07-24",
      "epss": "0.00127",
      "percentile": "0.02717"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-48523\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-05-28T16:16:29.280\",\"lastModified\":\"2026-06-17T10:55:03.693\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"jpadilla\",\"product\":\"pyjwt\",\"versions\":[{\"version\":\"\u003e= 2.9.0, \u003c 2.13.0\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N\",\"baseScore\":5.4,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":2.8,\"impactScore\":2.5}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-05-28T15:27:44.771049Z\",\"id\":\"CVE-2026-48523\",\"options\":[{\"exploitation\":\"poc\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-347\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"2.9.0\",\"versionEndExcluding\":\"2.12.1\",\"matchCriteriaId\":\"AD0759FF-955F-482B-9EB8-C2F445D540E4\"}]}]}],\"references\":[{\"url\":\"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Exploit\",\"Vendor Advisory\"]},{\"url\":\"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f\",\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"tags\":[\"Exploit\",\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-16T02:17:40+00:00",
      "cve": "CVE-2026-48523",
      "id": "CVE-2026-48523",
      "initial_release_date": "2026-05-28T15:10:19.141000+00:00",
      "product_status:known_affected": "179",
      "product_status:known_not_affected": "19",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "python-pyjwt: PyJWT: Verifier-side algorithm bypass leads to unauthorized information access",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48523.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"cna\": {\"title\": \"PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys\", \"problemTypes\": [{\"descriptions\": [{\"cweId\": \"CWE-347\", \"lang\": \"en\", \"description\": \"CWE-347: Improper Verification of Cryptographic Signature\", \"type\": \"CWE\"}]}], \"metrics\": [{\"cvssV3_1\": {\"attackComplexity\": \"LOW\", \"attackVector\": \"NETWORK\", \"availabilityImpact\": \"NONE\", \"baseScore\": 5.4, \"baseSeverity\": \"MEDIUM\", \"confidentialityImpact\": \"LOW\", \"integrityImpact\": \"LOW\", \"privilegesRequired\": \"LOW\", \"scope\": \"UNCHANGED\", \"userInteraction\": \"NONE\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N\", \"version\": \"3.1\"}}], \"references\": [{\"name\": \"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f\", \"tags\": [\"x_refsource_CONFIRM\"], \"url\": \"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f\"}], \"affected\": [{\"vendor\": \"jpadilla\", \"product\": \"pyjwt\", \"versions\": [{\"version\": \"\u003e= 2.9.0, \u003c 2.13.0\", \"status\": \"affected\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-05-28T15:10:19.141Z\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.\"}], \"source\": {\"advisory\": \"GHSA-jq35-7prp-9v3f\", \"discovery\": \"UNKNOWN\"}}, \"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-48523\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-05-28T15:27:44.771049Z\"}}}], \"references\": [{\"url\": \"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f\", \"tags\": [\"exploit\"]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-05-28T15:27:32.358Z\"}}]}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-48523\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"state\": \"PUBLISHED\", \"assignerShortName\": \"GitHub_M\", \"dateReserved\": \"2026-05-21T16:18:10.619Z\", \"datePublished\": \"2026-05-28T15:10:19.141Z\", \"dateUpdated\": \"2026-05-28T15:27:49.780Z\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • 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.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.