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CVE-2026-48526— PyJWT: Public-key JWK accepted as HMAC secret enables forged HS256 tokens when mixed families are allowed

Quick assessment

Affected
jpadilla pyjwt
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

pyjwt是美国José Padilla个人开发者的一个 Python 库。允许对 JSON Web 令牌（JWT）进行编码和解码。 pyjwt 2.13.0之前版本存在数据伪造问题漏洞，该漏洞源于验证器在解码JSON Web令牌时，同时支持非对称和HMAC算法，但未验证JSON Web密钥在HMAC算法中的使用，导致攻击者可以使用发行者公钥作为HMAC算法的密钥。

CVSS 7.4 · High EPSS 0.43% · P35

Possible ATT&CK Techniques 1 AI

T1556 · Modify Authentication Process

Affected Version Matrix 1

VendorProduct Version RangeStatus
jpadilla pyjwt < 2.13.0 affected
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I. Basic Information for CVE-2026-48526

Vulnerability Information
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Vulnerability Title
PyJWT: Public-key JWK accepted as HMAC secret enables forged HS256 tokens when mixed families are allowed
Source: CVE Program / CVE List V5
Vulnerability Description
PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, when the verifier is decoding JSON Web Tokens, while supporting both asymmetric and HMAC algorithms, the library does not validate use of JSON Web Keys in HMAC algorithm, allowing attacker to use the issuer public key as the secret key for HMAC algorithm. This vulnerability is fixed in 2.13.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
pyjwt 数据伪造问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
pyjwt是美国José Padilla个人开发者的一个 Python 库。允许对 JSON Web 令牌（JWT）进行编码和解码。 pyjwt 2.13.0之前版本存在数据伪造问题漏洞，该漏洞源于验证器在解码JSON Web令牌时，同时支持非对称和HMAC算法，但未验证JSON Web密钥在HMAC算法中的使用，导致攻击者可以使用发行者公钥作为HMAC算法的密钥。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
jpadilla pyjwt < 2.13.0 -

II. Public POCs for CVE-2026-48526

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 11211 chars
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III. Intelligence Information for CVE-2026-48526

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Vendor Advisories for CVE-2026-48526 (1)

Same Patch Batch · jpadilla · 2026-05-28 · 5 CVEs total

CVE-2026-48523 5.4 MEDIUM PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys
CVE-2026-48525 5.3 MEDIUM PyJWT: Unauthenticated DoS via unbounded Base64URL decoding of unused payload segment in b
CVE-2026-48522 4.2 MEDIUM PyJWKClient: missing scheme allowlist enables SSRF + token forgery via file://, ftp://, da
CVE-2026-48524 3.7 LOW PyJWT: PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (Do

IV. Related Vulnerabilities

Same product: pyjwt
Same vendor: jpadilla
Same weakness: CWE-287

V. Comments for CVE-2026-48526

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