CVE-2026-0621

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.0%, top 85% 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, nvd
Trending — 3 sources updated this weekElevated
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Anthropic's MCP TypeScript SDK versions up to and including 1.25.1 contain a regular expression denial of service (ReDoS) vulnerability in the UriTemplate class when processing RFC 6570 exploded array patterns. The dynamically generated regular expression used during URI matching contains nested quantifiers that can trigger catastrophic backtracking on specially crafted inputs, resulting in excessive CPU consumption. An attacker can exploit this by supplying a malicious URI that causes the Node.js process to become unresponsive, leading to a denial of service.

CVSS v3
7.5
EG Score
7.5(medium)
EPSS
32.2%
KEV
Not listed

Published

January 5, 2026

Last Modified

July 14, 2026

Advisory Details (2)

Auto-updated Jul 15, 2026
🔬 Proof of concept available. No patch confirmed yet.
generic🟡 PoC Available

MCP TypeScript SDK UriTemplate ReDoS · Issue #965 · modelcontextprotocol/typescript-sdk · GitHub

https://github.com/modelcontextprotocol/typescript-sdk/issues/965
generic

MCP TypeScript SDK UriTemplate Exploded Array Pattern ReDoS | Advisories | VulnCheck

https://www.vulncheck.com/advisories/mcp-typescript-sdk-uritemplate-exploded-array-pattern-redos

Vendor Advisories for CVE-2026-0621(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)
npm(1)
PackageVulnerable rangeFixed inDependents
@modelcontextprotocol/sdk—1.25.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 40× 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.

  1. 2026-07-15 16:57 UTCEPSS rescore
  2. 2026-07-15 02:00 UTCEPSS rescore
  3. 2026-07-14 17:20 UTCNVD updateCVSS v3 → 7.5
  4. 2026-07-14 16:10 UTCMITRE cvelistV5CVSS v3 → 8.7
  5. 2026-07-13 22:30 UTCEPSS rescore
  6. 2026-07-13 06:12 UTCEPSS rescore
  7. 2026-07-12 05:46 UTCEPSS rescore
  8. 2026-07-11 08:27 UTCEPSS rescore
  9. 2026-07-09 19:10 UTCEPSS rescore
  10. 2026-07-08 15:15 UTCEPSS rescore
  11. 2026-07-08 15:15 UTCEPSS rescore
  12. 2026-07-07 13:46 UTCEPSS rescore
  13. 2026-07-06 16:27 UTCEPSS rescore
  14. 2026-07-06 06:32 UTCOSV refresh
  15. 2026-07-06 02:23 UTCEPSS rescore
  16. 2026-07-05 02:30 UTCEPSS rescore
  17. 2026-07-05 02:30 UTCEPSS rescore
  18. 2026-07-04 06:31 UTCEPSS rescore
  19. 2026-07-01 15:06 UTCEPSS rescore
  20. 2026-07-01 15:06 UTCEPSS rescore
  21. 2026-06-30 23:22 UTCEPSS rescore
  22. 2026-06-29 14:06 UTCEPSS rescore
  23. 2026-06-28 14:07 UTCEPSS rescore
  24. 2026-06-28 04:56 UTCEPSS rescore
  25. 2026-06-28 04:56 UTCEPSS rescore
Show 49 more
  1. 2026-06-27 03:08 UTCEPSS rescore
  2. 2026-06-25 13:49 UTCEPSS rescore
  3. 2026-06-24 14:05 UTCEPSS rescore
  4. 2026-06-23 21:32 UTCEPSS rescore
  5. 2026-06-22 14:25 UTCEPSS rescore
  6. 2026-06-22 14:25 UTCEPSS rescore
  7. 2026-06-21 14:56 UTCEPSS rescore
  8. 2026-06-21 14:56 UTCEPSS rescore
  9. 2026-06-21 01:59 UTCEPSS rescore
  10. 2026-06-21 01:59 UTCEPSS rescore
  11. 2026-06-19 19:25 UTCEPSS rescore
  12. 2026-06-18 17:52 UTCEPSS rescore
  13. 2026-06-17 18:05 UTCOSV refresh
  14. 2026-06-17 17:53 UTCEPSS rescore
  15. 2026-06-16 17:52 UTCEPSS rescore
  16. 2026-06-15 17:48 UTCEPSS rescore
  17. 2026-06-14 23:18 UTCEPSS rescore
  18. 2026-06-13 23:00 UTCEPSS rescore
  19. 2026-06-13 23:00 UTCEPSS rescore
  20. 2026-06-12 23:12 UTCEPSS rescore
  21. 2026-06-11 14:00 UTCEPSS rescore
  22. 2026-06-10 22:18 UTCEPSS rescore
  23. 2026-06-10 13:22 UTCEPSS rescore
  24. 2026-06-08 14:17 UTCEPSS rescore
  25. 2026-06-08 14:17 UTCEPSS rescore
  26. 2026-06-07 15:25 UTCEPSS rescore
  27. 2026-06-07 15:24 UTCEPSS rescore
  28. 2026-06-06 13:47 UTCEPSS rescore
  29. 2026-06-06 13:47 UTCEPSS rescore
  30. 2026-06-06 13:47 UTCEPSS rescore
  31. 2026-06-05 22:47 UTCEPSS rescore
  32. 2026-06-05 06:10 UTCEPSS rescore
  33. 2026-06-05 06:10 UTCEPSS rescore
  34. 2026-06-04 13:12 UTCEPSS rescore
  35. 2026-06-04 13:12 UTCEPSS rescore
  36. 2026-06-04 13:12 UTCEPSS rescore
  37. 2026-06-02 20:13 UTCEPSS rescore
  38. 2026-06-02 20:13 UTCEPSS rescore
  39. 2026-06-01 13:51 UTCEPSS rescore
  40. 2026-06-01 13:51 UTCEPSS rescore
  41. 2026-06-01 13:51 UTCEPSS rescore
  42. 2026-05-31 22:30 UTCEPSS rescore
  43. 2026-05-31 22:30 UTCEPSS rescore
  44. 2026-05-31 00:16 UTCEPSS rescore
  45. 2026-05-31 00:16 UTCEPSS rescore
  46. 2026-05-31 00:16 UTCEPSS rescore
  47. 2026-05-29 16:41 UTCEG score recompute
  48. 2026-05-29 13:44 UTCEPSS rescore
  49. 2026-05-29 13:44 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-0621?
CVE-2026-0621 is a high vulnerability published on January 5, 2026. Anthropic's MCP TypeScript SDK versions up to and including 1.25.1 contain a regular expression denial of service (ReDoS) vulnerability in the UriTemplate class when processing RFC 6570 exploded array patterns. The dynamically generated regular expression used during URI matching contains nested…
When was CVE-2026-0621 disclosed?
CVE-2026-0621 was first published in the National Vulnerability Database on January 5, 2026, with the most recent update on July 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-0621 actively exploited?
CVE-2026-0621 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 32.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-0621?
CVE-2026-0621 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-0621?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-0621, 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-2026-0621

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