CVE-2026-44452

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 66% 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
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.9Exploit: None knownExposed: 0

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

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 8dc37cb, when h2o receives a ClientHello message over TLS or QUIC and it contains a zero-length SNI extension, the h2o server runs over the zero-length hostname while trying to copy the hostname, assuming that it is NULL-terminated. This is a potential denial-of-service attack vector in sense that it might trigger segmentation violation. This issue has been fixed by commit 8dc37cb.

CVSS v3
5.9
EG Score
5.9(medium)
EG Risk
27(Track)
EG Risk 27/100SSVC: 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
Severity59% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
35%
KEV
Not listed

Published

July 16, 2026

Last Modified

August 6, 2026

Advisory Details (1)

Auto-updated Jul 16, 2026
Patch available. Sources: github.
github Patch Available

heap overrun · Advisory · h2o/h2o · GitHub

https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvq

Affected Packages

(2 across 2 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
h2o2.2.5+dfsg2-10 ... 2.2.5+dfsg2-9 (10 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
h2o2.2.5+dfsg2-10 ... 2.2.5+dfsg2-9 (7 versions)——

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 43× 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. 2026-09-11 14:53 UTCEPSS rescore
  2. 2026-09-11 09:37 UTCEPSS rescore
  3. 2026-09-10 09:34 UTCEPSS rescore
  4. 2026-09-08 22:00 UTCEPSS rescore
  5. 2026-09-08 00:23 UTCEG score recompute
  6. 2026-09-07 16:01 UTCEPSS rescore
  7. 2026-09-06 13:47 UTCEPSS rescore
  8. 2026-09-05 20:32 UTCEG score recompute
  9. 2026-09-04 05:06 UTCEPSS rescore
  10. 2026-09-02 14:12 UTCEPSS rescore
  11. 2026-09-01 13:54 UTCEPSS rescore
  12. 2026-08-31 03:05 UTCEG score recompute
  13. 2026-08-30 19:17 UTCEPSS rescore
  14. 2026-08-30 03:27 UTCEG score recompute
  15. 2026-08-30 01:22 UTCEPSS rescore
  16. 2026-08-28 21:41 UTCEPSS rescore
  17. 2026-08-27 14:25 UTCEPSS rescore
  18. 2026-08-27 12:23 UTCEG score recompute
  19. 2026-08-26 14:46 UTCEPSS rescore
  20. 2026-08-26 07:29 UTCEG score recompute
  21. 2026-08-25 13:49 UTCEPSS rescore
  22. 2026-08-25 07:31 UTCEG score recompute
  23. 2026-08-23 07:39 UTCEG score recompute
  24. 2026-08-23 00:19 UTCEPSS rescore
  25. 2026-08-22 08:03 UTCEG score recompute
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  1. 2026-08-21 23:49 UTCEPSS rescore
  2. 2026-08-21 08:26 UTCEG score recompute
  3. 2026-08-20 22:55 UTCEPSS rescore
  4. 2026-08-20 08:49 UTCEG score recompute
  5. 2026-08-19 17:04 UTCEPSS rescore
  6. 2026-08-19 09:13 UTCEG score recompute
  7. 2026-08-18 13:48 UTCEPSS rescore
  8. 2026-08-18 09:35 UTCEG score recompute
  9. 2026-08-17 13:47 UTCEPSS rescore
  10. 2026-08-17 09:48 UTCEG score recompute
  11. 2026-08-16 14:56 UTCEPSS rescore
  12. 2026-08-16 10:11 UTCEG score recompute
  13. 2026-08-16 02:14 UTCEPSS rescore
  14. 2026-08-15 10:35 UTCEG score recompute
  15. 2026-08-15 01:30 UTCEPSS rescore
  16. 2026-08-14 10:59 UTCEG score recompute
  17. 2026-08-13 22:00 UTCEPSS rescore
  18. 2026-08-13 11:22 UTCEG score recompute
  19. 2026-08-12 13:51 UTCEPSS rescore
  20. 2026-08-12 11:46 UTCEG score recompute
  21. 2026-08-11 13:43 UTCEPSS rescore
  22. 2026-08-11 12:09 UTCEG score recompute
  23. 2026-08-11 00:00 UTCEPSS rescore
  24. 2026-08-10 12:32 UTCEG score recompute
  25. 2026-08-09 13:46 UTCEPSS rescore
  26. 2026-08-09 12:56 UTCEG score recompute
  27. 2026-08-08 16:37 UTCEPSS rescore
  28. 2026-08-08 13:20 UTCEG score recompute
  29. 2026-08-06 14:07 UTCEG score recompute
  30. 2026-08-06 13:46 UTCEPSS rescore
  31. 2026-08-06 07:42 UTCEG score recompute
  32. 2026-08-05 19:17 UTCEPSS rescore
  33. 2026-08-05 08:05 UTCEG score recompute
  34. 2026-08-04 15:10 UTCEPSS rescore
  35. 2026-08-04 10:38 UTCEPSS rescore
  36. 2026-08-04 08:29 UTCEG score recompute
  37. 2026-08-03 10:36 UTCEPSS rescore
  38. 2026-08-02 09:09 UTCEG score recompute
  39. 2026-08-02 02:27 UTCEPSS rescore
  40. 2026-08-01 09:33 UTCEG score recompute
  41. 2026-08-01 04:16 UTCEPSS rescore
  42. 2026-07-31 09:56 UTCEG score recompute
  43. 2026-07-30 16:28 UTCEPSS rescore
  44. 2026-07-30 10:19 UTCEG score recompute
  45. 2026-07-30 01:30 UTCEPSS rescore
  46. 2026-07-29 10:43 UTCEG score recompute
  47. 2026-07-28 15:36 UTCEPSS rescore
  48. 2026-07-28 11:05 UTCEG score recompute
  49. 2026-07-27 14:13 UTCEPSS rescore
  50. 2026-07-27 11:00 UTCEG score recompute
  51. 2026-07-26 14:54 UTCEPSS rescore
  52. 2026-07-26 14:54 UTCEPSS rescore
  53. 2026-07-26 11:23 UTCEG score recompute
  54. 2026-07-25 14:18 UTCEPSS rescore
  55. 2026-07-24 14:17 UTCEPSS rescore
  56. 2026-07-23 14:18 UTCEPSS rescore
  57. 2026-07-23 03:15 UTCEG score recompute
  58. 2026-07-22 14:08 UTCEPSS rescore
  59. 2026-07-21 15:24 UTCEPSS rescore
  60. 2026-07-20 17:08 UTCEPSS rescore
  61. 2026-07-19 14:31 UTCEPSS rescore
  62. 2026-07-19 02:32 UTCEG score recompute
  63. 2026-07-19 02:29 UTCEPSS rescore
  64. 2026-07-18 10:04 UTCEPSS rescore
  65. 2026-07-17 14:12 UTCEG score recompute
  66. 2026-07-16 23:43 UTCEG score recompute
  67. 2026-07-16 23:43 UTCNVD updatefirst tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-44452?
CVE-2026-44452 is a medium vulnerability published on July 16, 2026. h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 8dc37cb, when h2o receives a ClientHello message over TLS or QUIC and it contains a zero-length SNI extension, the h2o server runs over the zero-length hostname while trying to copy the hostname, assuming that it is…
When was CVE-2026-44452 disclosed?
CVE-2026-44452 was first published in the National Vulnerability Database on July 16, 2026, with the most recent update on August 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-44452 actively exploited?
CVE-2026-44452 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 65.3% of all scored CVEs.
What is the CVSS score of CVE-2026-44452?
CVE-2026-44452 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2026-44452?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-44452, 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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