Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-102270— PyJWT: ReDoS vulnerability when calling the `is_pem_format` function.

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 标准的一种 Python 实现。在 2.14.0 版本之前，PyJWT 中的 is_pem_format 函数存在漏洞，原因是其用于匹配 PEM 格式的惰性正则表达式会发生大量回溯。当类似证书的输入中包含重复出现的 BEGIN 标记但没有对应的 END 标记时，就会触发该问题。在这种情况下，is_pem_format 函数在搜索 PEM 结束标记时会进行无界回溯，从而导致攻击者可以利用此漏洞造成严重的 CPU 资源消耗。该问题已在 2.14.0 版本中修复。

CVSS 4.4 · Medium

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-102270

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
PyJWT: ReDoS vulnerability when calling the `is_pem_format` function.
Source: CVE Program / CVE List V5
Vulnerability Description
PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, PyJWT is_pem_format is affected because lazy PEM regular expression backtracks extensively. This occurs when a certificate-like input contains repeated BEGIN markers without a matching END marker. As a result, is_pem_format performs unbounded backtracking while searching for a PEM end marker. Consequently, an attacker can cause intensive CPU consumption. This issue is fixed in version 2.14.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
jpadilla pyjwt < 2.14.0 -

II. Public POCs for CVE-2026-102270

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-102270

请登录查看更多情报信息。

Other References for CVE-2026-102270 (3)

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

CVE-2026-102268 9.1 CRITICAL PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip th
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

IV. Related Vulnerabilities

Same product: pyjwt
Same vendor: jpadilla
Same weakness: CWE-1333

V. Comments for CVE-2026-102270

No comments yet

Leave a comment