Public proof of conceptFix available

CVE-2026-48525

Q: Is CVE-2026-48525 actively exploited?

A proof-of-concept exploit exists for CVE-2026-48525, but active exploitation has not been confirmed at this time.

Q: What is the CVSS score for CVE-2026-48525?

CVE-2026-48525 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

A public proof of concept exists; no exploitation attested.

Published2026-05-28
WeaknessCWE-400

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2026-05-2816:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-48525?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-48525?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV

Pyjwt project pyjwt

Branch	Affected	Fixed in	Source
2.x	≥ 2.8.0, ≤ 2.12.1	no fix published	NVD

pyjwt

Branch	Affected	Fixed in	Source
2.x	≥ 2.8.0, < 2.13.0	2.13.0	OSV

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

github.comMitigation · Vendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVE recordread 2026-10-23
CISA-ADPSSVC decisionpoc2026-05-28
OpenCVESSVC decisionpoc—
CNACVSS 3.15.3read 2026-10-23
CNAweakness (CWE)CWE-400read 2026-10-23
FIRST EPSSEPSS score0.4 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Published: 2026-05-28
Last Modified: 2026-06-17
NVD status: Analyzed

Frequently asked questions

What is CVE-2026-48525?

Is CVE-2026-48525 actively exploited?

A proof-of-concept exploit exists for CVE-2026-48525, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-48525?

CVE-2026-48525 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

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