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Medium severity5.3NVD Advisory· Published May 28, 2026· Updated Jun 1, 2026

CVE-2026-48525

CVE-2026-48525

Description

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.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
pyjwtPyPI
>= 2.8.0, < 2.13.02.13.0

Affected products

62

Patches

Vulnerability mechanics

References

4

News mentions

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