Moto: joserfc has Possible Uncontrolled Resource Consumption Vulnerability Triggered by Logging Arbitrarily Large JWT
Affects motoSource GCVE Database
Not known to be exploited · CVSS 9.2 Critical : upgrade to 5.1.17 as a priority.
Data as of 30 Oct 2026, 06:59 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.1.17
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:HExploitation evidence
Disclosed: evidence found.
CVE published 18 Nov 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade moto to 5.1.17.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewmotopkg:brew/motoOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available in joserfc version 5.1.17; upgrading to this version is recommended. Additionally, ensure that the web server or reverse proxy (e.g., nginx, uvicorn with appropriate settings) enforces strict limits on HTTP header sizes to prevent large JWT tokens from reaching the application. Applications running without a production-grade server or reverse proxy should implement such limits to mitigate this issue. No other specific mitigations are indicated by the vendor advisory.
Description
The joserfc Python JWT library has a vulnerability where logging error messages embeds non-decoded JWT token parts, allowing an attacker to cause uncontrolled resource consumption by sending arbitrarily large JWT bearer tokens. This can lead to excessively large log entries and memory usage during token decoding, especially if the web application is not protected by a production-grade web server or reverse proxy that enforces header size limits. The issue arises because the library raises an ExceededSizeError exception containing the full large payload, which is already loaded in memory. The vulnerability affects joserfc versions >=5.1.13 and <5.1.17 and is fixed in version 5.1.17.
References
- github.com/authlib/joserfc/security/advisories/GHSA-frfh-8v73-gjg4 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2025-65015 (opens in a new tab)
- github.com/authlib/joserfc/commit/63932f169d924caffafa761af2122b82059017f7 (opens in a new tab)
- github.com/authlib/joserfc/commit/673c8743fd0605b0e1de6452be6cba75f44e466b (opens in a new tab)
- github.com/authlib/joserfc (opens in a new tab)
- github.com/authlib/joserfc/releases/tag/1.3.5 (opens in a new tab)
- github.com/authlib/joserfc/releases/tag/1.4.2 (opens in a new tab)
- github.com/pypa/advisory-database/tree/main/vulns/joserfc/PYSEC-2026-361.yaml (opens in a new tab)
- pypi.org/project/joserfc (opens in a new tab)