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CVE-2026-102268— PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard

Quick assessment

Affected
jpadilla pyjwt
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

PyJWT 是 JSON Web Token 标准的 Python 实现。在 2.14.0 版本之前，jwt/utils.py 中的 is_pem_format 函数存在缺陷，因为它无法识别 cryptography 加载器所接受的所有 PEM 格式。当应用程序混合使用 HMAC 和非对称算法，并将经过篡改的非对称公钥以原始字节形式提供时，就会触发此问题。结果是，HMACAlgorithm.prepare_key 会将无法识别的非对称公钥误当作 HMAC 密钥使用。因此，攻击者只要知道公钥，就可以伪造经过 HMAC

CVSS 9.1 · Critical

Possible ATT&CK Techniques 1 AI

T1552.004 · Private Keys
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I. Basic Information for CVE-2026-102268

Vulnerability Information
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Vulnerability Title
PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard
Source: CVE Program / CVE List V5
Vulnerability Description
PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, is_pem_format in jwt/utils.py is affected because is_pem_format does not recognize every PEM representation accepted by the cryptography loader. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a mutated public-key PEM as raw key bytes. As a result, HMACAlgorithm.prepare_key treats the unrecognized asymmetric public key as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
密码学签名的验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
jpadilla pyjwt < 2.14.0 -

II. Public POCs for CVE-2026-102268

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III. Intelligence Information for CVE-2026-102268

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Other References for CVE-2026-102268 (3)

Same Patch Batch · jpadilla · 2026-09-28 · 13 CVEs total

CVE-2026-102266 7.4 HIGH PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
CVE-2026-102267 7.4 HIGH PyJWT: PyJWKClient follows redirects when fetching JWKS
CVE-2026-102271 7.4 HIGH PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217
CVE-2026-102272 7.4 HIGH PyJWT BOM Bypass
CVE-2026-102273 7.4 HIGH PyJWT accepts public JWK containers as HMAC secrets
CVE-2026-102275 6.5 MEDIUM PyJWT accepts inconsistent OKP x/d JWKs, causing public/private key identity confusion
CVE-2026-102274 5.9 MEDIUM PyJWT: Malformed RSA JWK aborts parsing of an entire JWK Set
CVE-2026-101918 5.3 MEDIUM PyJWT: Unauthenticated RecursionError DoS in pre-verification payload parse (PyJWKClient.g
CVE-2026-101917 5.3 MEDIUM PyJWT: PyJWKClient still amplifies unauthenticated JWKS fetches on unknown kid values (inc
CVE-2026-102265 5.3 MEDIUM PyJWT: Uncaught RecursionError in jwt.decode() on deeply nested token header
CVE-2026-102269 4.8 MEDIUM PyJWT: Non-canonical signature segments enable raw-token revocation bypass
CVE-2026-102270 4.4 MEDIUM PyJWT: ReDoS vulnerability when calling the `is_pem_format` function.

IV. Related Vulnerabilities

Same product: pyjwt
Same vendor: jpadilla
Same weakness: CWE-347

V. Comments for CVE-2026-102268

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