CVE-2026-49953

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2026-06-15. a secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Elevated
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.5Exploit: NoneExposed: 0

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

Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical character recognition model against collected CAPTCHA samples to reliably predict challenge text, bypassing protections on login, registration, and other functionality from automated abuse.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
—
EPSS
28.4%
KEV
Not listed

Published

June 15, 2026

Last Modified

June 16, 2026

Advisory Details (3)

Auto-updated Jun 15, 2026
🔬 Proof of concept available. No patch confirmed yet.
generic

Discuz! X5.0 CAPTCHA Bypass via Predictable Character Set | Advisories | VulnCheck

https://www.vulncheck.com/advisories/discuz-x5-0-captcha-bypass-via-predictable-character-set
generic🟡 PoC Available

Chaining Security Bugs in Discuz! X5.0: from Race Condition to Pre-Auth RCE | Karma(In)Security

https://karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rce
generic🟡 PoC Available

Discuz! <= X5.0 OCR-based CAPTCHA Bypass Vulnerability | Karma(In)Security

https://karmainsecurity.com/KIS-2026-10

Vendor Advisories for CVE-2026-49953(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 59× 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. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:25 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:31 UTCEPSS rescore
  5. 2026-07-19 14:31 UTCEPSS rescore
  6. 2026-07-19 02:29 UTCEPSS rescore
  7. 2026-07-18 10:04 UTCEPSS rescore
  8. 2026-07-16 17:03 UTCEPSS rescore
  9. 2026-07-16 14:40 UTCGHSA enrichment
  10. 2026-07-15 16:57 UTCEPSS rescore
  11. 2026-07-15 16:57 UTCEPSS rescore
  12. 2026-07-15 15:47 UTCGHSA enrichment
  13. 2026-07-15 02:00 UTCEPSS rescore
  14. 2026-07-14 14:21 UTCGHSA enrichment
  15. 2026-07-13 22:30 UTCEPSS rescore
  16. 2026-07-13 15:45 UTCGHSA enrichment
  17. 2026-07-13 06:13 UTCEPSS rescore
  18. 2026-07-12 17:08 UTCGHSA enrichment
  19. 2026-07-12 05:46 UTCEPSS rescore
  20. 2026-07-11 18:13 UTCGHSA enrichment
  21. 2026-07-11 08:27 UTCEPSS rescore
  22. 2026-07-10 19:35 UTCGHSA enrichment
  23. 2026-07-09 21:02 UTCGHSA enrichment
  24. 2026-07-09 19:10 UTCEPSS rescore
  25. 2026-07-08 21:28 UTCGHSA enrichment
Show 55 more
  1. 2026-07-08 15:16 UTCEPSS rescore
  2. 2026-07-07 22:53 UTCGHSA enrichment
  3. 2026-07-07 13:46 UTCEPSS rescore
  4. 2026-07-07 00:20 UTCGHSA enrichment
  5. 2026-07-06 16:27 UTCEPSS rescore
  6. 2026-07-06 02:23 UTCEPSS rescore
  7. 2026-07-05 17:36 UTCGHSA enrichment
  8. 2026-07-05 02:30 UTCEPSS rescore
  9. 2026-07-04 18:59 UTCGHSA enrichment
  10. 2026-07-04 06:31 UTCEPSS rescore
  11. 2026-07-03 17:49 UTCGHSA enrichment
  12. 2026-07-02 19:14 UTCGHSA enrichment
  13. 2026-07-01 20:41 UTCGHSA enrichment
  14. 2026-07-01 15:07 UTCEPSS rescore
  15. 2026-06-30 23:22 UTCEPSS rescore
  16. 2026-06-30 22:05 UTCGHSA enrichment
  17. 2026-06-29 23:29 UTCGHSA enrichment
  18. 2026-06-29 14:06 UTCEPSS rescore
  19. 2026-06-29 14:06 UTCEPSS rescore
  20. 2026-06-29 00:55 UTCGHSA enrichment
  21. 2026-06-28 14:07 UTCEPSS rescore
  22. 2026-06-28 04:56 UTCEPSS rescore
  23. 2026-06-28 04:56 UTCEPSS rescore
  24. 2026-06-28 02:21 UTCGHSA enrichment
  25. 2026-06-27 03:47 UTCGHSA enrichment
  26. 2026-06-27 03:08 UTCEPSS rescore
  27. 2026-06-26 05:13 UTCGHSA enrichment
  28. 2026-06-25 13:49 UTCEPSS rescore
  29. 2026-06-25 06:39 UTCGHSA enrichment
  30. 2026-06-24 14:05 UTCEPSS rescore
  31. 2026-06-24 08:02 UTCGHSA enrichment
  32. 2026-06-23 21:33 UTCEPSS rescore
  33. 2026-06-23 21:33 UTCEPSS rescore
  34. 2026-06-23 09:27 UTCGHSA enrichment
  35. 2026-06-22 14:25 UTCEPSS rescore
  36. 2026-06-22 14:25 UTCEPSS rescore
  37. 2026-06-22 10:42 UTCGHSA enrichment
  38. 2026-06-21 14:56 UTCEPSS rescore
  39. 2026-06-21 14:56 UTCEPSS rescore
  40. 2026-06-21 11:40 UTCGHSA enrichment
  41. 2026-06-21 01:59 UTCEPSS rescore
  42. 2026-06-21 01:59 UTCEPSS rescore
  43. 2026-06-20 12:55 UTCGHSA enrichment
  44. 2026-06-19 19:26 UTCEPSS rescore
  45. 2026-06-19 19:26 UTCEPSS rescore
  46. 2026-06-19 14:21 UTCGHSA enrichment
  47. 2026-06-18 17:52 UTCEPSS rescore
  48. 2026-06-18 17:52 UTCEPSS rescore
  49. 2026-06-18 15:46 UTCGHSA enrichment
  50. 2026-06-17 17:53 UTCEPSS rescore
  51. 2026-06-17 16:57 UTCGHSA enrichment
  52. 2026-06-16 17:56 UTCGHSA enrichment
  53. 2026-06-16 17:53 UTCEPSS rescore
  54. 2026-06-15 19:19 UTCEG score recompute
  55. 2026-06-15 19:19 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-49953?
CVE-2026-49953 is a medium vulnerability published on June 15, 2026. Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical…
When was CVE-2026-49953 disclosed?
CVE-2026-49953 was first published in the National Vulnerability Database on June 15, 2026, with the most recent update on June 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-49953 actively exploited?
CVE-2026-49953 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 28.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-49953?
CVE-2026-49953 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-49953?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-49953, 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

Explore the affected products and dependency analysis for CVE-2026-49953

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