Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
jpadilla pyjwt — PyJWT: Unauthenticated DoS via unbounded Base64URL decoding of unused payload segment in b64=false detached JWS
AV AC PR UI S C I A CVSS EPSS %ile KEV
N L N N U N N L 5.3 .0037 30.3 —
AFFECTED
Product Versions Fixed
pyjwt >= 2.8.0, < 2.13.0 – —
TIMELINE
May 21 Reserved by GitHub_M
May 28 EXPLOIT PUBLISHED — CVE-2026-48525 (jpadilla pyjwt). Public exploit reference added.
May 28 Published (CNA: GitHub_M)
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.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
|---|
| May 21, 2026 | Reserved | Reserved by GitHub_M |
| May 28, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-48525 (jpadilla pyjwt). Public exploit reference added. |
| May 28, 2026 | Published | Published (CNA: GitHub_M) |
Affected
Affected products and packages — 1 row
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| jpadilla | pyjwt | — | >= 2.8.0, < 2.13.0 | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-48525 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.