CVE-2026-40396

MEDIUMNVD 4.04.0—
EchelonGraph scoreMEDIUM confidence

Score 4.0 from GitHub Security Advisory published 2026-04-12. NVD baseline CVSS 4.0; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
4.0
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 4.0Exploit: NoneExposed: 0

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

Varnish Cache 9 before 9.0.1 allows a "workspace overflow" denial of service (daemon panic) after timeout_linger. A malicious client could send an HTTP/1 request, wait long enough until the session releases its worker thread (timeout_linger) and resume traffic before the session is closed (timeout_idle) sending more than one request at once to trigger a pipelining operation between requests. This vulnerability affecting Varnish Cache 9.0.0 emerged from a port of the Varnish Enterprise non-blocking architecture for HTTP/2. New code was needed to adapt to a more recent workspace API that formalizes the pipelining operation. In addition to the workspace change on the Varnish Cache side, other differences created merge conflicts, like partial support for trailers in Varnish Enterprise. The conflict resolution missed one code path configuring pipelining to perform a complete workspace rollback, losing the guarantee that prefetched data would fit inside workspace_client during the transition from one request to the next. This can result in a workspace overflow, triggering a panic and crashing the Varnish server.

CVSS v3
4.0
EG Score
4.0(medium)
EG Risk
—
EPSS
27.1%
KEV
Not listed

Published

April 12, 2026

Last Modified

April 17, 2026

References (2)

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 35× 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 15:24 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-20 12:02 UTCOSV refresh
  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. 2026-07-15 16:57 UTCEPSS rescore
  10. 2026-07-15 16:57 UTCEPSS rescore
  11. 2026-07-15 02:00 UTCEPSS rescore
  12. 2026-07-13 22:30 UTCEPSS rescore
  13. 2026-07-13 06:13 UTCEPSS rescore
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  15. 2026-07-12 05:46 UTCEPSS rescore
  16. 2026-07-11 08:27 UTCEPSS rescore
  17. 2026-07-09 19:10 UTCEPSS rescore
  18. 2026-07-08 15:15 UTCEPSS rescore
  19. 2026-07-07 13:46 UTCEPSS rescore
  20. 2026-07-06 16:27 UTCEPSS rescore
  21. 2026-07-06 16:27 UTCEPSS rescore
  22. 2026-07-06 02:23 UTCEPSS rescore
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  24. 2026-07-05 02:30 UTCEPSS rescore
  25. 2026-07-04 06:31 UTCEPSS rescore
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  1. 2026-07-01 15:06 UTCEPSS rescore
  2. 2026-06-30 23:22 UTCEPSS rescore
  3. 2026-06-29 14:06 UTCEPSS rescore
  4. 2026-06-28 14:07 UTCEPSS rescore
  5. 2026-06-28 04:56 UTCEPSS rescore
  6. 2026-06-27 03:08 UTCEPSS rescore
  7. 2026-06-25 13:49 UTCEPSS rescore
  8. 2026-06-25 13:49 UTCEPSS rescore
  9. 2026-06-24 14:05 UTCEPSS rescore
  10. 2026-06-23 21:33 UTCEPSS rescore
  11. 2026-06-22 14:25 UTCEPSS rescore
  12. 2026-06-22 14:25 UTCEPSS rescore
  13. 2026-06-21 14:56 UTCEPSS rescore
  14. 2026-06-21 14:56 UTCEPSS rescore
  15. 2026-06-21 01:59 UTCEPSS rescore
  16. 2026-06-19 19:25 UTCEPSS rescore
  17. 2026-06-18 17:52 UTCEPSS rescore
  18. 2026-06-18 17:52 UTCEPSS rescore
  19. 2026-06-17 17:53 UTCEPSS rescore
  20. 2026-06-16 17:52 UTCEPSS rescore
  21. 2026-06-15 17:49 UTCEPSS rescore
  22. 2026-06-14 22:03 UTCGHSA enrichment
  23. 2026-06-13 23:00 UTCEPSS rescore
  24. 2026-06-12 23:12 UTCEPSS rescore
  25. 2026-06-12 23:12 UTCEPSS rescore
  26. 2026-06-11 19:45 UTCGHSA enrichment
  27. 2026-06-11 14:00 UTCEPSS rescore
  28. 2026-06-10 22:18 UTCEPSS rescore
  29. 2026-06-10 13:22 UTCEPSS rescore
  30. 2026-06-10 13:22 UTCEPSS rescore
  31. 2026-06-10 11:47 UTCGHSA enrichment
  32. 2026-06-09 11:26 UTCGHSA enrichment
  33. 2026-06-08 14:17 UTCEPSS rescore
  34. 2026-06-08 14:17 UTCEPSS rescore
  35. 2026-06-08 08:05 UTCGHSA enrichment
  36. 2026-06-07 15:25 UTCEPSS rescore
  37. 2026-06-07 15:25 UTCEPSS rescore
  38. 2026-06-07 07:44 UTCGHSA enrichment
  39. 2026-06-06 13:47 UTCEPSS rescore
  40. 2026-06-06 13:47 UTCEPSS rescore
  41. 2026-06-05 22:47 UTCEPSS rescore
  42. 2026-06-05 06:10 UTCEPSS rescore
  43. 2026-06-05 06:10 UTCEPSS rescore
  44. 2026-06-04 13:12 UTCEPSS rescore
  45. 2026-06-04 13:12 UTCEPSS rescore
  46. 2026-06-02 23:07 UTCGHSA enrichment
  47. 2026-06-02 20:13 UTCEPSS rescore
  48. 2026-06-01 22:46 UTCGHSA enrichment
  49. 2026-06-01 13:52 UTCEPSS rescore
  50. 2026-06-01 13:52 UTCEPSS rescore
  51. 2026-06-01 13:51 UTCEPSS rescore
  52. 2026-05-31 22:30 UTCEPSS rescore
  53. 2026-05-31 22:30 UTCEPSS rescore
  54. 2026-05-31 00:16 UTCEPSS rescore
  55. 2026-05-31 00:16 UTCEPSS rescore
  56. 2026-05-31 00:16 UTCEPSS rescore
  57. 2026-05-29 13:44 UTCEPSS rescore
  58. 2026-05-29 13:44 UTCEPSS rescore
  59. 2026-05-28 13:44 UTCEPSS rescore
  60. 2026-05-28 13:44 UTCEPSS rescore
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  62. 2026-05-27 13:40 UTCEPSS rescore
  63. 2026-05-27 13:40 UTCEPSS rescore
  64. 2026-05-27 13:40 UTCEPSS rescore
  65. 2026-05-26 13:44 UTCEPSS rescore
  66. 2026-05-26 07:18 UTCEPSS rescore
  67. 2026-05-26 07:18 UTCEPSS rescore
  68. 2026-05-20 22:38 UTCEPSS rescore
  69. 2026-05-20 22:38 UTCEPSS rescore
  70. 2026-05-20 17:44 UTCEG score recompute
  71. 2026-05-20 17:44 UTCGHSA enrichment
  72. 2026-05-20 11:22 UTCEPSS rescore
  73. 2026-05-20 11:22 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-40396?
CVE-2026-40396 is a medium vulnerability published on April 12, 2026. Varnish Cache 9 before 9.0.1 allows a "workspace overflow" denial of service (daemon panic) after timeoutlinger. A malicious client could send an HTTP/1 request, wait long enough until the session releases its worker thread (timeoutlinger) and resume traffic before the session is closed…
When was CVE-2026-40396 disclosed?
CVE-2026-40396 was first published in the National Vulnerability Database on April 12, 2026, with the most recent update on April 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-40396 actively exploited?
CVE-2026-40396 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 27.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-40396?
CVE-2026-40396 has a CVSS v3 base score of 4.0 (NVD).
How do I remediate CVE-2026-40396?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-40396, 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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