CVE-2025-62706

6.5 MEDIUM 0.5% exploit odds Fix listed Denial of service Library

What it is

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.5, Authlib’s JWE zip=DEF path performs unbounded DEFLATE decompression. A very small ciphertext can expand into tens or hundreds of megabytes on decrypt, allowing an attacker who can supply decryptable tokens to exhaust memory and CPU and cause denial of service. This issue has been patched in version 1.6.5. Workarounds for this issue involve rejecting or stripping zip=DEF for inbound JWEs at the application boundary, forking and add a bounded decompression guard via decompressobj().decompress(data, MAX_SIZE)) and returning an error when output exceeds a safe limit, or enforcing strict maximum token sizes and fail fast on oversized inputs; combine with rate limiting.

At a glance

Exploitability: Can be exploited over the network with a low-privilege account. High risk of service disruption.
Exploit odds: 0.5% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2025-10-22 22:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-19 13:10 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.5% in the next 30 days (EPSS).
Severity: 6.5 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2025-10-22 22:15 UTC
Last modified: 2026-10-19 13:10 UTC
Exploit probability: 0.5% · EPSS, next 30 days
Weakness: CWE-400 · Uncontrolled resource consumption
Record status: Modified

Affected

Authlib < 1.6.5

Attack profile CVSS 3.1 · 6.5

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Is it in your code?

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Fix and advisories

References

NVD record · CVE.org record