joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign and HMACAlgorithm.verify in src/joserfc/_rfc7518/jws_algs.py pass the output of OctKey.get_op_key(...) to hmac.new(...) and OctKey.import_key in src/joserfc/_rfc7518/oct_key.py only emits a SecurityWarning for keys shorter than 14 bytes without rejecting zero-length input. This issue is fixed in version 1.6.8.
CVE-2026-49852
HIGHPre-NVD 8.78.7—Trending — 3 sources updated this weekElevated
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 91% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
8.7
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.7Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 8.7
- EG Score
- 8.7(medium)
- EPSS
- 9.4%
- KEV
- Not listed
Published
July 2, 2026
Last Modified
July 20, 2026
Advisory Details (3)
Auto-updated Jul 17, 2026🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_release.
github_release Patch Available
1.6.8
Patch available: authlib/joserfc 1.6.8
https://github.com/authlib/joserfc/releases/tag/1.6.8github_commit Patch Available
commit 86d00910b2b2 (authlib/joserfc)
Patch available: authlib/joserfc 1.6.8 (contains commit 86d00910b2b2)
https://github.com/authlib/joserfc/commit/86d00910b2b2d2d07503fee9b572906daefab7f1github Patch Available🟡 PoC Available
joserfc: HS256/HS384/HS512 verify accepts empty/nil HMAC key (cross-language sibling of CVE-2026-45363) · Advisory · authlib/joserfc · GitHub
https://github.com/authlib/joserfc/security/advisories/GHSA-gg9x-qcx2-xmrhVendor Advisories for CVE-2026-49852(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| joserfc | 0.1.0 ... 1.6.7 (40 versions) | 1.6.8 | — |
Weakness Classification(3)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 10× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-20 17:08 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 03:51 UTCEG score recompute
- 2026-07-19 02:29 UTCEPSS rescore
- 2026-07-17 19:26 UTCEG score recompute▲ 8.70
- 2026-07-17 19:24 UTCMITRE cvelistV5CVSS v3 → 8.7 · CVSS v4 → 8.7
- 2026-07-02 20:07 UTCEG score recompute
Related CVEs(same CWE)
Same CWE
10 shownCWE-287 · CWE-326
Frequently asked(5)
What is CVE-2026-49852?
CVE-2026-49852 is a high vulnerability published on July 2, 2026. joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign…
When was CVE-2026-49852 disclosed?
CVE-2026-49852 was first published in the National Vulnerability Database on July 2, 2026, with the most recent update on July 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-49852 actively exploited?
CVE-2026-49852 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 9.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-49852?
CVE-2026-49852 has a CVSS v3 base score of 8.7 (NVD).
How do I remediate CVE-2026-49852?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-49852, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-49852
Is Your Infrastructure Affected by CVE-2026-49852?
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