PyJWKClient: missing scheme allowlist enables SSRF + token forgery via file://, ftp://, data: schemes
PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib's default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch. If an application's jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem), cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface), or forge tokens that PyJWT verifies as valid. The library does not directly return non-HTTP(S) URI contents to the attacker; the chained "plant a JWKS to forge tokens" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. This vulnerability is fixed in 2.13.0.
- Published
- May 28, 2026
- Updated
- Jun 17, 2026
- EPSS
- 0.2% · 11th percentile
- CWE
- CWE-441
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Report tools
Action score
16
Monitor
Low priority for now.
- CVSS
- 16 / 40 · 4.2 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- proof of concept
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · GitHub_M
- 4.2
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| pyjwt project | pyjwt | cpe:2.3:a:pyjwt_project:pyjwt |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- pyjwt project pyjwtbefore 2.13.0
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
jpadilla pyjwt
- < 2.13.0affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | pyjwt | all versions | — |
| Debian:14 | pyjwt | before 2.13.0-1 | 2.13.0-1 |
| openSUSE:Leap 16.0 | python-PyJWT | before 2.12.1-160000.2.1 | 2.12.1-160000.2.1 |
| openSUSE:Tumbleweed | python-PyJWT | before 2.13.0-1.1 | 2.13.0-1.1 |
| PyPI | pyjwt | from 2.0.0 · before 2.13.0 | 2.13.0 |
| PyPI | pyjwt | before 2.13.0 | 2.13.0 |
| SUSE:Linux Enterprise Micro 5.5 | python-PyJWT | before 2.4.0-150200.3.14.1 | 2.4.0-150200.3.14.1 |
| SUSE:Linux Enterprise Module for Public Cloud 15 SP4 | python-PyJWT | before 2.8.0-150400.8.13.1 | 2.8.0-150400.8.13.1 |
| SUSE:Linux Enterprise Server 16.0 | python-PyJWT | before 2.12.1-160000.2.1 | 2.12.1-160000.2.1 |
| SUSE:Linux Micro 6.0 | python-PyJWT | before 2.9.0-3.1 | 2.9.0-3.1 |
| SUSE:Linux Micro 6.1 | python-PyJWT | before 2.12.1-slfo.1.1_2.1 | 2.12.1-slfo.1.1_2.1 |
Same product
pyjwt project: all recordsOther highest-scoring records for the same primary product.
- CVE-2017-11424In PyJWT 1.5.0 and below the `invalid_strings` check in `HMACAlgorithm.prepare_key` does not account for all PEM encoded public keys.31Monitor
- CVE-2026-32597PyJWT accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)30Monitor
- CVE-2024-53861Issuer field partial matches allowed in pyjwt30Monitor
- CVE-2022-29217Key confusion through non-blocklisted public key formats in PyJWT30Monitor
- CVE-2026-48526PyJWT: Public-key JWK accepted as HMAC secret enables forged HS256 tokens when mixed families are allowed29Monitor
- CVE-2025-45768pyjwt v2.10.1 was discovered to contain weak encryption.28Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| jpadilla pyjwt | 2.13.0 · description | Vendor (CNA) |
| debian:pyjwt | 2.13.0-1 · Debian:14 | Package registry (OSV) |
| opensuse:python-PyJWT | 2.13.0-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| PyPI:pyjwt | 2.13.0 | Package registry (OSV) |
| suse:python-PyJWT | 2.12.1-slfo.1.1_2.1 · SUSE:Linux Micro 6.1 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- A user must open a link or visit a page.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- low · data can be read
- Integrity
- low · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-441 · Unintended Proxy or Intermediary ('Confused Deputy')CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
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