Vulnerability in pyjwt (CVE-2026-101917)
Summary
Vulnerability in pyjwt (CVE-2026-101917). Risk of unauthorized operations or information disclosure. Exploitable via kid. Mitigation: upgrade to 2.13.0 or later.
Original description
The description as published by the source.
Summary
CVE-2026-48524 (GHSA-fhv5-28vv-h8m8, "PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (DoS)") was fixed in 2.13.0 by stopping fetch_data() from clearing the cache on a fetch error. That closed one amplification path but did not add the mitigation the advisory's title implies: there is still no rate-limit, negative-cache, or minimum-refresh-interval for unknown kids.
At HEAD, get_signing_key(kid) (jwt/jwks_client.py:185-211), on any unknown kid, calls get_signing_keys(refresh=True), and refresh=True bypasses jwk_set_cache unconditionally and forces a fresh fetch_data(). The kid is read from the unverified token header (get_signing_key_from_jwt decodes with verify_signature=False), so no valid token and no authentication is required. lru_cache does not cache the raised exception, so even the same unknown kid repeated re-fetches on every call.
Affected
pyjwt <= 2.13.0 (the latest release; the patched release for CVE-2026-48524). No fixed version yet.
Proof of concept (verified on 2.13.0, cache enabled = realistic prod config)
import threading, http.server, socketserver, json
from jwt import PyJWKClient
hits = {'n': 0}
JWKS = json.dumps({"keys":[{"kty":"oct","kid":"real","k":"AAAA"}]}).encode()
class H(http.server.BaseHTTPRequestHandler):
def do_GET(self):
hits['n'] += 1
self.send_response(200); self.send_header('Content-Type','application/json'); self.end_headers()
self.wfile.write(JWKS)
def log_message(s…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-101917 has been found in pyjwt.
Attackers can target a specific entry point like kid over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade pyjwt to 2.13.0 or later.
If unsure, ask your IT team or search "pyjwt CVE-2026-101917" on the vendor's site.
CVE-2026-101917 (pyjwt) — CWE-770 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: kid / master / ba4853a / PyJWKClient
Patched: 2.13.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-770) exists in pyjwt. Attackers reach the vulnerable code path via kid without authentication.
Check the vendor advisory for the affected versions of pyjwt. Attack surface: kid / master / ba4853a / PyJWKClient.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 2.13.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'pyjwt' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'pyjwt' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
pyjwtを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade pyjwt to 2.13.0ステージング環境で 2.13.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-101917 pyjwt
- Ubuntu UBUNTU-CVE-2026-101917 pyjwt
References
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- package pypi.org
- web github.com
- web github.com
- web github.com