CVE-2026-21868

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 81% 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 week
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.

Flag Forge is a Capture The Flag (CTF) platform. Versions 2.3.2 and below have a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint (/api/user/[username]). The application constructs a regular expression dynamically using unescaped user input (the username parameter). An attacker can exploit this by sending a specially crafted username containing regex meta-characters (e.g., deeply nested groups or quantifiers), causing the MongoDB regex engine to consume excessive CPU resources. This can lead to Denial of Service for other users. The issue is fixed in version 2.3.3. To workaround this issue, implement a Web Application Firewall (WAF) rule to block requests containing regex meta-characters in the URL path.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

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
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
18.7%
KEV
Not listed

Published

January 8, 2026

Last Modified

January 20, 2026

References (1)

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 49× 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. 2026-07-23 14:18 UTCEPSS rescore
  2. 2026-07-23 14:18 UTCEPSS rescore
  3. 2026-07-23 11:19 UTCOSV refresh
  4. 2026-07-23 03:06 UTCEG score recompute
  5. 2026-07-22 14:08 UTCEPSS rescore
  6. 2026-07-21 15:24 UTCEPSS rescore
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  1. 2026-07-11 08:27 UTCEPSS rescore
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  3. 2026-07-08 15:15 UTCEPSS rescore
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  5. 2026-07-07 13:46 UTCEPSS rescore
  6. 2026-07-06 16:27 UTCEPSS rescore
  7. 2026-07-06 16:27 UTCEPSS rescore
  8. 2026-07-06 06:02 UTCOSV refresh
  9. 2026-07-06 02:23 UTCEPSS rescore
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  21. 2026-06-27 03:08 UTCEPSS rescore
  22. 2026-06-25 13:49 UTCEPSS rescore
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  24. 2026-06-23 21:32 UTCEPSS rescore
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  27. 2026-06-21 14:56 UTCEPSS rescore
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  31. 2026-06-19 19:25 UTCEPSS rescore
  32. 2026-06-18 17:52 UTCEPSS rescore
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  34. 2026-06-17 17:44 UTCOSV refresh
  35. 2026-06-16 17:52 UTCEPSS rescore
  36. 2026-06-15 17:48 UTCEPSS rescore
  37. 2026-06-14 23:18 UTCEPSS rescore
  38. 2026-06-13 23:00 UTCEPSS rescore
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  41. 2026-06-11 14:00 UTCEPSS rescore
  42. 2026-06-10 22:18 UTCEPSS rescore
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  44. 2026-06-08 14:17 UTCEPSS rescore
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  46. 2026-06-07 15:25 UTCEPSS rescore
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  48. 2026-06-06 13:47 UTCEPSS rescore
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  54. 2026-06-04 13:12 UTCEPSS rescore
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  67. 2026-05-29 16:30 UTCEG score recompute
  68. 2026-05-29 13:44 UTCEPSS rescore
  69. 2026-05-29 13:44 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-21868?
CVE-2026-21868 is a high vulnerability published on January 8, 2026. Flag Forge is a Capture The Flag (CTF) platform. Versions 2.3.2 and below have a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint (/api/user/[username]). The application constructs a regular expression dynamically using unescaped user input (the username…
When was CVE-2026-21868 disclosed?
CVE-2026-21868 was first published in the National Vulnerability Database on January 8, 2026, with the most recent update on January 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-21868 actively exploited?
CVE-2026-21868 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 18.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-21868?
CVE-2026-21868 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-21868?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-21868, 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.

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