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PyJWT CVE-2026-48525

| EUVDEUVD-2026-32919 MEDIUM
Uncontrolled Resource Consumption (CWE-400)
2026-05-28 GitHub_M GHSA-w7vc-732c-9m39 PYSEC-2026-178
Python Denial Of Service Red Hat
5.3
CVSS 3.1 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
SUSE
MEDIUM
qualitative
Red Hat
5.3 MEDIUM
qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

2
Patch available
May 28, 2026 - 17:01 EUVD
Analysis Generated
May 28, 2026 - 15:50 vuln.today

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 391 pypi packages depend on pyjwt (261 direct, 130 indirect)

Ecosystem-wide dependent count for version 2.8.0.

DescriptionGitHub Advisory

PyJWT is a JSON Web Token implementation in Python. From 2.8.0 to 2.12.1, when verifying detached JWS tokens using the unencoded-payload option ("b64": false, RFC 7797), PyJWT performs Base64URL decoding of the compact-serialization payload segment before enforcing the detached-payload rules. For b64=false, PyJWT later discards that decoded payload and replaces it with the caller-provided detached_payload. In practice, this turns the middle segment into an attacker-controlled “work amplifier”: a remote client can supply an arbitrarily large Base64URL payload segment that forces CPU work + memory allocations even if the signature is invalid. This creates an unauthenticated DoS vector against any endpoint that verifies detached JWS using PyJWT. This vulnerability is fixed in 2.13.0.

AnalysisAI

Uncontrolled resource consumption in PyJWT 2.8.0-2.12.1 exposes any service that verifies detached JWS tokens to unauthenticated denial-of-service. When the unencoded-payload extension (b64=false, RFC 7797) is in use, PyJWT unnecessarily Base64URL-decodes the compact-serialization payload segment before discarding it in favor of the caller-supplied detached payload - turning that segment into an attacker-controlled amplifier for CPU and memory exhaustion regardless of signature validity. No public exploit has been identified at time of analysis, but the CVSS vector (AV:N/AC:L/PR:N/UI:N) confirms fully unauthenticated remote exploitation against any affected endpoint using this feature.

Technical ContextAI

PyJWT (CPE: cpe:2.3:a:jpadilla:pyjwt:*:*:*:*:*:*:*:*) is the most widely used Python library for creating and verifying JSON Web Tokens. RFC 7797 defines the JWS Unencoded Payload Option, signified by the b64=false header claim, which allows JWS compact serializations to carry a detached payload passed out-of-band. The defect (CWE-400: Uncontrolled Resource Consumption) arises because PyJWT's verification path performs Base64URL decoding of the inline compact-serialization payload segment prior to applying the b64=false detached-payload enforcement logic. Since that decoded value is subsequently overwritten by the legitimate detached_payload, there is zero functional justification for the early decode - yet the CPU cycles and memory allocations consumed by decoding an arbitrarily large attacker-supplied segment are fully realized. The fix in 2.13.0 guards against this by skipping or size-limiting the decode step when the b64=false header is present.

RemediationAI

The primary fix is to upgrade PyJWT to version 2.13.0 or later, which resolves the premature Base64URL decode in the detached JWS verification path. The vendor advisory is available at https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39. If an immediate upgrade is not feasible, the most effective compensating control is to audit all call sites that invoke PyJWT's JWT decode or verify functions and confirm whether the detached_payload parameter is passed alongside tokens containing a b64=false header; if that code path is not actively used, ensure it cannot be reached from unauthenticated input. For endpoints that must retain detached JWS support, adding an application-layer payload size limit (e.g., rejecting incoming compact serializations exceeding a defined byte threshold before they reach PyJWT) reduces the amplification window, though this does not eliminate the underlying flaw. Blocking or rate-limiting the relevant API endpoints at the network perimeter is a lower-fidelity workaround with the trade-off of degraded availability for legitimate clients.

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 12 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Micro 5.5 Fixed
SUSE Linux Enterprise Module for Basesystem 15 SP7 Fixed

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CVE-2026-48525 vulnerability details – vuln.today
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