Vulnerability in joserfc (CVE-2026-48990)
Summary
Vulnerability in joserfc (CVE-2026-48990). Risk of unauthorized operations or information disclosure. Exploitable via joserfc. Mitigation: upgrade to 1.6.7 or later.
Original description
The description as published by the source.
RFC7797 b64=false JWS payloads bypass JWSRegistry payload-size limits during deserialization
Summary
Testing revealed that joserfc accepts oversized RFC7797 b64=false JWS payloads without applying JWSRegistry.max_payload_length.
The normal JWS compact and flattened JSON paths reject payloads above the configured payload-size limit with ExceededSizeError. The RFC7797 unencoded payload paths do not make the same check. A valid b64=false compact or flattened JSON JWS can therefore deserialize successfully with a payload larger than JWSRegistry.max_payload_length.
This creates a moderate availability/resource-exhaustion risk for applications that accept lower-trust JWS values and rely on joserfc to reject oversized token content during verification.
Affected Product
- Package:
joserfc - Ecosystem:
pip - Audited release:
1.6.5 - Audit tag:
1.6.5 - Audit commit:
881712980934fb601bed26fe3ae1ec0b7780e6f7 - Tested affected releases:
1.3.4,1.3.5,1.4.2,1.6.2,1.6.3,1.6.4,1.6.5 - Fixed release: none known
Vulnerability Details
In joserfc 1.6.5, the default JWS registry has max_payload_length = 128000 and exposes validate_payload_size().
The normal compact extraction path calls that check before base64url-decoding the payload. The RFC7797 compact path validates the header and signature segment sizes, then assigns the unencoded payload directly:
if is_rfc7797_enabled(protected):
if not payload_segment and pay…
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-2026-48990 has been found in joserfc.
Attackers can target a specific entry point like joserfc over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade joserfc to 1.6.7 or later.
If unsure, ask your IT team or search "joserfc CVE-2026-48990" on the vendor's site.
CVE-2026-48990 (joserfc) — CWE-400 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: joserfc / JWSRegistry.max_payload_length / ExceededSizeError / pip
Patched: 1.6.7 — apply immediately
Workaround: Before a fixed release is available, affected applications can reduce exposure by rejecting oversized serialized JWS inputs before passing them to joserfc, disabling or disallowing RFC7797 b64=false tokens if not needed, and enforcing strict requ
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-400) exists in joserfc. Attackers reach the vulnerable code path via joserfc without authentication.
Check the vendor advisory for the affected versions of joserfc. Attack surface: joserfc / JWSRegistry.max_payload_length / ExceededSizeError / pip.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 1.6.7.
Workaround: Before a fixed release is available, affected applications can reduce exposure by rejecting oversized serialized JWS inputs before passing them to joserfc, disabling or disallowing RFC7797 b64=false tokens if not needed, and enforcing strict requ
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'joserfc' . 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 'joserfc' . | 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
joserfcを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Before a fixed release is available, affected applications can reduce exposure by rejecting oversized serialized JWS inputs before passing them to `joserfc`, disabling or disallowing RFC7797 `b64=false` tokens if not needed, and enforcing strict requパッチが適用されるまでの応急処置として、Before a fixed release is available, affected applications can reduce exposure by rejecting oversized serialized JWS inputs before passing them to
joserfc, disabling or disallowing RFC7797b64=falsetokens if not needed, and enforcing strict requ を実施。回避策の副作用 (機能低下) を確認した上で。 -
3Apply patch patch
Upgrade joserfc to 1.6.7ステージング環境で 1.6.7 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。
-
4Post-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-2026-48990 joserfc
- Ubuntu UBUNTU-CVE-2026-48990 joserfc
References
- web github.com
- web github.com
- web nvd.nist.gov
- web github.com