CVE-2026-28490Public exploitNetwork attack vector

JWE plaintext recovery via RSA1_5 exception oracle

Published Mar 16, 2026 · Updated Mar 16, 2026

Padding oracle in Authlib before 1.6.9 allows remote attackers to recover JWE content through crafted RSA1_5 tokens. RSAAlgorithm.unwrap checks the decrypted content-encryption-key length and raises ValueError before AES-GCM validation, distinguishing bad padding from a bad tag. Exploitation requires a reachable JWE decryption endpoint and many observable responses; recovered keys expose intercepted payloads and permit token forgery.

CVSS severity8.3
High
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Padding oracle in Authlib before 1.6.9 allows remote attackers to recover JWE content through crafted RSA1_5 tokens. RSAAlgorithm.unwrap checks the decrypted content-encryption-key length and raises ValueError before AES-GCM validation, distinguishing bad padding from a bad tag. Exploitation requires a reachable JWE decryption endpoint and many observable responses; recovered keys expose intercepted payloads and permit token forgery.

The record

CVE
CVE-2026-28490
Published
Mar 16, 2026
Updated
Mar 16, 2026
Vendor
Authlib
Product
Authlib
Classifications
CWE-203, CWE-327, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.6.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Authlib · Authlibversion=< 1.6.9

Published CVSS scores

8.3GitHubCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
6.5NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-203Observable Discrepancy
CWE-327Use of a Broken or Risky Cryptographic Algorithm
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo