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Fencer Vulns
medium 5.3

CVE-2026-48990 json

joserfc: b64=false RFC7797 JWS payloads bypass JWSRegistry payload-size limits during deserialization

published 2026-06-17 4 mo ago modified 2026-10-26 13 d ago also GHSA-wphv-vfrh-23q5 , PYSEC-2026-2530 , EUVD-2026-37805

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. In versions 1.3.4 through 1.6.5, joserfc accepts oversized RFC7797 b64=false JWS payloads without applying JWSRegistry.max_payload_length, which can lead to resource exhaustion. 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. Applications that accept lower-trust JWS values and rely on joserfc to reject oversized token content during verification have a moderate availability risk. This issue has been fixed in version 1.6.7.

Patch / fix

  • pypi joserfc 1.6.7
  • joserfc Debian 14 1.6.8-1

debian advisories DEBIAN-CVE-2026-48990

  • jaeger hummingbird 1 2.19.0-1.hum1

red hat advisories RHSA-2026:25039

  • python-joserfc openSUSE Tumbleweed 1.7.1-1.1

opensuse advisories openSUSE-SU-2026:11067-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-48990 updated cvss 5.3

joserfc: joserfc: Resource exhaustion via oversized JSON Web Signature (JWS) payloads

  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26/lightspeed-chatbot-rhel9 1785646188
    fixed: vendor fix “The risk can be mitigated by rejecting oversized serialized JWS inputs before they reach joserfc and enforcing strict request/body size limits at the application or reverse-proxy layer.” RHSA-2026:50479
  • Red Hat Ansible Automation Platform 2.7 ansible-automation-platform-27/lightspeed-chatbot-rhel9 1785426734
    fixed: vendor fix “The risk can be mitigated by rejecting oversized serialized JWS inputs before they reach joserfc and enforcing strict request/body size limits at the application or reverse-proxy layer.” RHSA-2026:50340
  • Red Hat Hardened Images jaeger 2.19.0-1.hum1
    fixed: vendor fix “The risk can be mitigated by rejecting oversized serialized JWS inputs before they reach joserfc and enforcing strict request/body size limits at the application or reverse-proxy layer.” RHSA-2026:25039
  • Red Hat Migration Toolkit for Applications 8.2 mta/mta-solution-server-rhel9 1784109883
    fixed: vendor fix “The risk can be mitigated by rejecting oversized serialized JWS inputs before they reach joserfc and enforcing strict request/body size limits at the application or reverse-proxy layer.” RHSA-2026:43038
  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26/hub-rhel9 1785753568, ansible-automation-platform-26/gateway-rhel9 1785780020, ansible-automation-platform-26/hub-web-rhel9 1785756951, ansible-automation-platform-26/receptor-rhel9 1785632117, ansible-automation-platform-26/mcp-tools-rhel9 1785633968, ansible-automation-platform-26/controller-rhel9 1785753810, +24 more Red Hat Ansible Automation Platform 2.7 ansible-automation-platform-27/hub-rhel9 1785376164, ansible-automation-platform-27/gateway-rhel9 1785435970, ansible-automation-platform-27/hub-web-rhel9 1785379466, ansible-automation-platform-27/receptor-rhel9 1785389482, ansible-automation-platform-27/mcp-tools-rhel9 1785374970, ansible-automation-platform-27/controller-rhel9 1785378052, +25 more Red Hat Migration Toolkit for Applications 8.2 mta/mta-ui-rhel9 1783962515, mta/mta-cli-rhel9 1784211378, mta/mta-hub-rhel9 1784059743, mta/mta-rhel9-operator 1784219586, mta/mta-operator-bundle 1784220119, mta/mta-analyzer-addon-rhel9 1784163267, +7 more Red Hat Satellite 6 satellite/foreman-mcp-server-rhel9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/authlib/joserfc/security/advisories/GHSA-wphv-vfrh-23q5 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
pypi joserfc
>=1.3.4, <1.6.7
1.6.7

Affected products

  • authlib joserfc

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.