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Full vulnerability report · 2026
CVE-2026-101918High confidence

PyJWT: Unauthenticated RecursionError DoS in pre-verification payload parse (PyJWKClient.get_signing_key_from_jwt / verify_signature=False)

jpadilla · pyjwt

Official source article: GitHub GHSA-42VR-XJ54-VC7V ↗. Check the applicable product and release in the original source.

5.3MediumCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 96 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:High, raised one band.upgradedsince 29 Sep 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.29% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs jpadilla pyjwt and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 96 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

5 package states
Package result overrides the generic status

BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 2 affected package states shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.

Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcepyjwtAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 7 Oct 2026
Debian bookwormbookworm · sourcepyjwtAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 7 Oct 2026
Debian forkyforky · sourcepyjwtVendor fix publishedDebian records a fixed source-package version for this release.2.15.0-1Debian Security Tracker ↗Source updated 7 Oct 2026
Debian sidsid · sourcepyjwtVendor fix publishedDebian records a fixed source-package version for this release.2.15.0-1Debian Security Tracker ↗Source updated 7 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivepyjwtUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 7 Oct 2026
Open-source package ranges3 source-attributed ranges

These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.

Ecosystem and packageAffected rangeFirst fixed versionEvidence
PyPIpyjwtECOSYSTEM: introduced 2.0.0a1; fixed 2.15.02.15.0OSV record ↗aggregator derived · 1 Oct 2026
PyPIpyjwtECOSYSTEM: introduced 2.0.0a1; fixed 2.15.02.15.0OSV record ↗source linked ecosystem record · 1 Oct 2026
pipPyJWT>= 2.0.0a1, <= 2.14.02.15.0GitHub advisory ↗upstream repository advisory · 30 Sep 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

2 current
CVE-2026-101918 · CSAF 2.0 · revision 2 · interimSUSE Product Security TeamCVE-2026-101918
94 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • python-PyJWT as component of SUSE Linux Enterprise Desktop 15 SP7
  • python3-PyJWT as component of SUSE Linux Enterprise Desktop 15 SP7
  • python311-PyJWT as component of SUSE Linux Enterprise Desktop 15 SP7
  • python-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • python3-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • python-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP3
  • python3-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP3
  • python-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS
  • python3-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS
  • python311-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS
  • python-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP4
  • python3-PyJWT as component of SUSE Linux Enterprise High Performance Computing 15 SP4
Summary
PyJWT is a Python implementation of JSON Web Token standards. From 2.0.0a1 until 2.15.0, PyJWT PyJWKClient.get_signing_key_from_jwt is affected because payload parser catches ValueError but not RecursionError. This occurs when an attacker-controlled recursively nested payload reaches json.loads. As a result, documented PyJWT exception handling does not contain the failure. Consequently, an unauthenticated request can raise an exception that may produce an HTTP 500 response. The advisory-defined affected implementation also includes jwt/api_jwt.py, verify_signature=False. This issue is fixed in version 2.15.0.
Remediation
No remediation text is recorded.
CVE-2026-101918 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitypyjwt: PyJWT: Denial of Service via deeply nested JSON token payload
4 known not affected

The vendor explicitly states that these products are not affected by this CVE.

  • jaeger.src as a component of Red Hat Hardened Images
  • llvm21.src as a component of Red Hat Hardened Images
  • rust.src as a component of Red Hat Hardened Images
  • swift-lang.src as a component of Red Hat Hardened Images
Summary
A flaw was found in PyJWT. When processing a JSON Web Token (JWT) prior to signature verification, the parser fails to properly handle deeply nested data, leading to an unhandled recursion error. A remote unauthenticated attacker could exploit this flaw by submitting a specially crafted token, causing the application to raise an unexpected server exception and resulting in a Denial of Service (DoS).
Remediation
No remediation text is recorded.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-88479

No EUVD known-exploited evidence

PyJWT is a Python implementation of JSON Web Token standards. From 2.0.0a1 until 2.15.0, PyJWT PyJWKClient.get_signing_key_from_jwt is affected because payload parser catches ValueError but not RecursionError. This occurs when an attacker-controlled recursively nested payload reaches json.loads. As a result, documented PyJWT exception handling does not contain the failure. Consequently, an unauthenticated request can raise an exception that may produce an HTTP 500 response. The advisory-defined affected implementation also includes jwt/api_jwt.py, verify_signature=False. This issue is fixed in version 2.15.0.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
5.3 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 96 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

PyJWT is a Python implementation of JSON Web Token standards. From 2.0.0a1 until 2.15.0, PyJWT PyJWKClient.get_signing_key_from_jwt is affected because payload parser catches ValueError but not RecursionError. This occurs when an attacker-controlled recursively nested payload reaches json.loads. As a result, documented PyJWT exception handling does not contain the failure. Consequently, an unauthenticated request can raise an exception that may produce an HTTP 500 response. The advisory-defined affected implementation also includes jwt/api_jwt.py, verify_signature=False. This issue is fixed in version 2.15.0.

What

PyJWT is a Python implementation of JSON Web Token standards. From 2.0.0a1 until 2.15.0, PyJWT PyJWKClient.get_signing_key_from_jwt is affected because payload parser catches ValueError but not RecursionError. This occurs when an attacker-controlled recursively nested payload reaches json.loads. As a result, documented PyJWT exception handling does not contain the failure. Consequently, an unauthenticated request can raise an exception that may produce an HTTP 500 response. The advisory-defined affected implementation also includes jwt/api_jwt.py, verify_signature=False. This issue is fixed in version 2.15.0.

Why

An exception is thrown from a function, but it is not caught.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

PyJWT is a Python implementation of JSON Web Token standards. From 2.0.0a1 until 2.15.0, PyJWT PyJWKClient.get_signing_key_from_jwt is affected because payload parser catches ValueError but not RecursionError. This occurs when an attacker-controlled recursively nested payload reaches json.loads. As a result, documented PyJWT exception handling does not contain the failure. Consequently, an unauthenticated request can raise an exception that may produce an HTTP 500 response. The advisory-defined affected implementation also includes jwt/api_jwt.py, verify_signature=False. This issue is fixed in version 2.15.0.

Why

An exception is thrown from a function, but it is not caught.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

CISA Vulnrichment records proof-of-concept exploitation in its SSVC data. BlackTree has not independently executed or validated exploit material.

Likely attack path
a network path → Uncaught Exception → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-248 ↗

CWE-248: Uncaught Exception. An exception is thrown from a function, but it is not caught.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.ALowAvailability impact: A successful attack can cause a limited loss.
Post-exploitation / living off the land
Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
NetworkUnauthenticatedCWE-248Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-88479Official EUVD mapping

PyJWT is a Python implementation of JSON Web Token standards. From 2.0.0a1 until 2.15.0, PyJWT PyJWKClient.get_signing_key_from_jwt is affected because payload parser catches ValueError but not RecursionError. This occurs when an attacker-controlled recursively nested payload reaches json.loads. As a result, documented PyJWT exception handling does not contain the failure. Consequently, an unauthenticated request can raise an exception that may produce an HTTP 500 response. The advisory-defined affected implementation also includes jwt/api_jwt.py, verify_signature=False. This issue is fixed in version 2.15.0.

Official EUVD record ↗
CERT-FR · French · CERTFR-2026-AVI-1249Multiples vulnérabilités dans les produits VMware

ord?id=CVE-2025-61728 Référence CVE CVE-2025-61729 https://www.cve.org/CVERecord?id=CVE-2025-61729 Référence CVE CVE-2025-61730 https://www.cve.org/CVERecord?id=CVE-2025-61730 Référence CVE CVE-2025-61731 https://www.cve.org/CVERecord?id=CVE-2025-61731 Référence CVE CVE-2025-61732 https://www.cve.org/CVERecord?id=CVE-2025-61732 Référence CVE CVE-2025-68121 https://www.cve.org/CVERecord?id=CVE-2025-68121 Référence CVE CVE-2025-8869 https://www.cve.org/CVERecord?id=CVE-2025-8869 Référence CVE CVE-2026-0864 https://www.cve.org/CVERecord?id=CVE-2026-0864 Référence CVE CVE-2026-101917 https://www.cve.org/CVERecord?id=CVE-2026-101917 Référence CVE CVE-2026-101918 https://www.cve.org/CVERecord?id=CVE-2026-101918 Référence CVE CVE-2026-102265 https://www.cve.org/CVERecord?id=CVE-2026-102265 Référence CVE CVE-2026-102266 https://www.cve.org/CVERecord?id=CVE-2026-102266 Référence CVE CVE-2026-102267 https://www.cve.org/CVERecord?id=CVE-2026-102267 Référence CVE CVE-2026-102268 https://www.cve.org/CVERecord?id=CVE-2026-102268 Référence CVE CVE-2026-102269 https://www.cve.org/CVERecord?id=CVE-2026-102269 Référence CVE CVE-2026-102270 https://www.cve.org/CVERecord?id=CVE-2026-102270 Référence CVE CVE-2026-102271 https://www.cve.org/CVERecord?id=CVE-2026-102271 Référence CVE CVE-2026-102272 https://www.cve.o

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
Fixed
2.15.0.
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 28 Sept 2026 · Last source change 29 Sept 2026, 13:57 UTC · CWE-248 · Uncaught Exception

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-09-29
European sourceENISA EUVD · EUVD-2026-88479
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD awaiting enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Public exploit evidencePublic exploit evidence changed from No public exploit to Public exploit reference.
    Before
    No public exploit
    After
    Public exploit reference
    CVE.org ↗
  2. ENISA EUVD mappingEUVD-2026-88479 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-88479"}
    ENISA EUVD ↗
  3. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-88479↗Vendor CSAF · SUSE Product Security Team↗CISA Vulnrichment SSVC evidence↗CVE authority or vendor reference · GitHub GHSA-42VR-XJ54-VC7V↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-101918 · cve.blacktree.nl