CVE-2026-0621

HIGHNVD 7.57.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.4% (36th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Elevated
7.5EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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
7.5HIGHmedium confidence
EG Risk
65
EG Risk 65/100

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed (value × EchelonGraph’s weight)
Severity75% × 45%
The EG Score, 7.5 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.4%
EPSS %ILE
36th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

January 5, 2026

Last Modified

October 8, 2026

Advisory Details (2)

Auto-updated Jul 15, 2026
Patch available.
Web page

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

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

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 rangeFix by version rangeDependents
@modelcontextprotocol/sdk—
  • 1.3.0 up to 1.25.2: fixed in 1.25.2
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 27× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 98 of 160 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 2 repeat rows among the latest 100 are merged into the row they repeat. The 62 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-14 16:31 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  2. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  3. 2026-10-12 16:42 UTCEG score recompute
  4. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  5. 2026-10-11 20:17 UTCEG score recompute
  6. 2026-10-11 18:29 UTCEG score recompute
  7. 2026-10-11 15:03 UTCEG score recompute
  8. 2026-10-11 13:47 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  9. 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  10. 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  11. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  12. 2026-10-08 15:48 UTCEG score recompute
  13. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  14. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  15. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  16. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  17. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  18. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  19. 2026-09-30 15:02 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  20. 2026-09-29 15:20 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  21. 2026-09-28 13:50 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  22. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  23. 2026-09-23 13:47 UTCEPSS rescoreEPSS 0.4% · 38th percentile
  24. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.4% · 38th percentile
  25. 2026-09-19 07:06 UTCOSV refresh
Show 73 more
  1. 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.4% · 38th percentile
  2. 2026-09-16 05:14 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  3. 2026-09-13 16:46 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  4. 2026-09-12 15:00 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  5. 2026-09-11 14:52 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  6. 2026-09-11 09:36 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  7. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  8. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  9. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  10. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  11. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  12. 2026-09-02 14:11 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  13. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  14. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  15. 2026-08-31 10:34 UTCOSV refresh
  16. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  17. 2026-08-30 01:21 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  18. 2026-08-28 21:40 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  19. 2026-08-27 14:24 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  20. 2026-08-25 13:48 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  21. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  22. 2026-08-21 23:48 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  23. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  24. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  25. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  26. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  27. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  28. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  29. 2026-08-14 16:15 UTCEG score recompute
  30. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  31. 2026-08-12 13:50 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  32. 2026-08-11 13:42 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  33. 2026-08-10 23:59 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  34. 2026-08-09 21:53 UTCEG score recompute
  35. 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  36. 2026-08-08 16:37 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  37. 2026-08-08 02:03 UTCEG score recompute
  38. 2026-08-06 13:46 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  39. 2026-08-06 06:21 UTCEG score recompute
  40. 2026-08-05 19:17 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  41. 2026-08-04 15:09 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  42. 2026-08-04 10:38 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  43. 2026-08-03 10:35 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  44. 2026-08-02 02:26 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  45. 2026-08-01 04:15 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  46. 2026-07-30 16:27 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  47. 2026-07-30 01:30 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  48. 2026-07-28 15:36 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  49. 2026-07-27 14:13 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  50. 2026-07-26 14:54 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  51. 2026-07-25 14:17 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  52. 2026-07-24 14:17 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  53. 2026-07-23 14:18 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  54. 2026-07-23 11:19 UTCOSV refresh
  55. 2026-07-23 03:04 UTCEG score recompute
  56. 2026-07-22 14:08 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  57. 2026-07-21 15:24 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  58. 2026-07-20 17:08 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  59. 2026-07-19 14:30 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  60. 2026-07-19 02:28 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  61. 2026-07-18 10:04 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  62. 2026-07-16 17:02 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  63. 2026-07-15 16:57 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  64. 2026-07-15 02:00 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  65. 2026-07-14 17:20 UTCNVD updateCVSS v3 → 7.5
  66. 2026-07-14 16:10 UTCMITRE cvelistV5CVSS v3 → 8.7
  67. 2026-07-13 22:30 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  68. 2026-07-13 06:12 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  69. 2026-07-12 05:46 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  70. 2026-07-11 08:27 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  71. 2026-07-09 19:10 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  72. 2026-07-08 15:15 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  73. 2026-07-07 13:46 UTCEPSS rescoreEPSS 0.4% · 31st percentile

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-0621?
CVE-2026-0621 is a high-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-0621 published?
The CVE record for CVE-2026-0621 was published on January 5, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 8, 2026; the record at its source may have been updated since.
Is CVE-2026-0621 actively exploited?
CVE-2026-0621 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (36th percentile of EPSS-scored CVEs).
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?
A fix for CVE-2026-0621 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-0621 are linked in the Vendor Advisories panel on this page.

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