CVE-2026-43974

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.5%, top 61% 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
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0

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

Unexpected Status Code or Return Value vulnerability in ninenines gun (gun_http module) allows a malicious HTTP server to force the client into raw protocol mode via an unsolicited 101 Switching Protocols response.

In gun_http:handle_inform/8, when a 101 Switching Protocols response is received over HTTP/1.1, the function verifies only that the Upgrade header is syntactically valid and that the stream reference is a plain reference(). It does not check whether the client ever sent an Upgrade or Connection: upgrade header on the corresponding request. Because this check is absent, any 101 response (solicited or not) causes gun to dispatch a gun_upgrade message to the caller and transition the entire connection to raw protocol mode.

A malicious or compromised HTTP server can send an unsolicited 101 response to any HTTP/1.1 request, causing the gun client to abandon HTTP framing for that connection. Once in raw mode, gun_raw applies no flow control (flow=infinity) and re-arms socket active mode after every received packet, so the server can flood the client with arbitrary bytes. These are forwarded as unbounded gun_data messages to the owner process, exhausting its mailbox and BEAM memory, ultimately crashing the VM.

This issue affects gun: from 2.0.0 before 2.4.0.

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 PROB
0%
EPSS %ILE
39%
KEV
Not listed

Published

June 8, 2026

Last Modified

August 18, 2026

Advisory Details (3)

Auto-updated Jun 8, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
github_commit

commit 5b48068c29ce (ninenines/gun)

Fix landed in ninenines/gun commit 5b48068c29ce — awaiting tagged release

https://github.com/ninenines/gun/commit/5b48068c29ce5e112cb149b5857c7d4dc319a81b
generic

OSV - Open Source Vulnerabilities

https://osv.dev/vulnerability/EEF-CVE-2026-43974
generic

gun HTTP/1.1 client accepts unsolicited 101 Switching Protocols response allowing server-driven protocol hijack and OOM | Erlang Ecosystem Foundation CNA

https://cna.erlef.org/cves/CVE-2026-43974.html

Vendor Advisories for CVE-2026-43974(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)
Hex(1)
PackageVulnerable rangeFixed inDependents
gun2.0.0, 2.0.1, 2.1.0, 2.2.0, 2.3.02.4.0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 57× 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.

Showing the most recent 100 of 176 total refreshes for this CVE.

  1. 2026-08-25 13:49 UTCEPSS rescore
  2. 2026-08-25 01:33 UTCEG score recompute
  3. 2026-08-23 11:53 UTCEG score recompute
  4. 2026-08-23 00:19 UTCEPSS rescore
  5. 2026-08-21 23:49 UTCEPSS rescore
  6. 2026-08-21 07:58 UTCEG score recompute
  7. 2026-08-20 22:55 UTCEPSS rescore
  8. 2026-08-20 09:32 UTCEG score recompute
  9. 2026-08-19 17:04 UTCEPSS rescore
  10. 2026-08-18 16:58 UTCEG score recompute▼ 1.20
  11. 2026-08-18 15:59 UTCNVD updateCVSS v3 → 7.5
  12. 2026-08-18 13:48 UTCEPSS rescore
  13. 2026-08-17 13:47 UTCEPSS rescore
  14. 2026-08-17 01:58 UTCEG score recompute
  15. 2026-08-16 14:56 UTCEPSS rescore
  16. 2026-08-16 12:19 UTCEG score recompute
  17. 2026-08-16 02:14 UTCEPSS rescore
  18. 2026-08-15 12:02 UTCEG score recompute
  19. 2026-08-15 01:30 UTCEPSS rescore
  20. 2026-08-13 22:28 UTCEG score recompute
  21. 2026-08-13 22:00 UTCEPSS rescore
  22. 2026-08-12 19:10 UTCEG score recompute
  23. 2026-08-12 13:51 UTCEPSS rescore
  24. 2026-08-11 20:03 UTCEG score recompute
  25. 2026-08-11 13:43 UTCEPSS rescore
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  1. 2026-08-11 08:58 UTCEG score recompute
  2. 2026-08-11 00:00 UTCEPSS rescore
  3. 2026-08-09 23:49 UTCEG score recompute
  4. 2026-08-09 13:46 UTCEPSS rescore
  5. 2026-08-09 01:44 UTCEG score recompute
  6. 2026-08-08 16:37 UTCEPSS rescore
  7. 2026-08-07 16:37 UTCEG score recompute
  8. 2026-08-06 18:24 UTCEG score recompute
  9. 2026-08-06 13:46 UTCEPSS rescore
  10. 2026-08-05 20:17 UTCEG score recompute
  11. 2026-08-05 19:17 UTCEPSS rescore
  12. 2026-08-04 16:23 UTCEG score recompute
  13. 2026-08-04 15:10 UTCEPSS rescore
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  15. 2026-08-03 15:22 UTCEG score recompute
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  17. 2026-08-02 09:06 UTCEG score recompute
  18. 2026-08-02 02:27 UTCEPSS rescore
  19. 2026-08-01 10:54 UTCEG score recompute
  20. 2026-08-01 04:16 UTCEPSS rescore
  21. 2026-07-31 04:57 UTCEG score recompute
  22. 2026-07-30 16:28 UTCEPSS rescore
  23. 2026-07-30 01:30 UTCEPSS rescore
  24. 2026-07-29 06:29 UTCEG score recompute
  25. 2026-07-29 06:29 UTCGHSA enrichment
  26. 2026-07-28 15:36 UTCEPSS rescore
  27. 2026-07-28 02:55 UTCEG score recompute
  28. 2026-07-28 02:55 UTCGHSA enrichment
  29. 2026-07-27 14:13 UTCEPSS rescore
  30. 2026-07-27 08:53 UTCGHSA enrichment
  31. 2026-07-26 21:48 UTCEG score recompute
  32. 2026-07-26 21:47 UTCGHSA enrichment
  33. 2026-07-26 14:54 UTCEPSS rescore
  34. 2026-07-26 14:54 UTCEPSS rescore
  35. 2026-07-26 07:14 UTCEG score recompute
  36. 2026-07-26 07:14 UTCGHSA enrichment
  37. 2026-07-25 14:18 UTCEPSS rescore
  38. 2026-07-24 14:17 UTCEPSS rescore
  39. 2026-07-23 14:18 UTCEPSS rescore
  40. 2026-07-23 03:14 UTCEG score recompute
  41. 2026-07-22 14:08 UTCEPSS rescore
  42. 2026-07-21 15:24 UTCEPSS rescore
  43. 2026-07-20 17:08 UTCEPSS rescore
  44. 2026-07-19 14:31 UTCEPSS rescore
  45. 2026-07-19 02:29 UTCEPSS rescore
  46. 2026-07-18 10:04 UTCEPSS rescore
  47. 2026-07-16 17:03 UTCEPSS rescore
  48. 2026-07-16 09:48 UTCGHSA enrichment
  49. 2026-07-15 22:28 UTCGHSA enrichment
  50. 2026-07-15 16:57 UTCEPSS rescore
  51. 2026-07-15 02:00 UTCEPSS rescore
  52. 2026-07-14 13:53 UTCGHSA enrichment
  53. 2026-07-14 02:50 UTCGHSA enrichment
  54. 2026-07-13 22:30 UTCEPSS rescore
  55. 2026-07-13 06:13 UTCEPSS rescore
  56. 2026-07-12 11:34 UTCGHSA enrichment
  57. 2026-07-12 05:46 UTCEPSS rescore
  58. 2026-07-11 20:30 UTCGHSA enrichment
  59. 2026-07-11 09:26 UTCGHSA enrichment
  60. 2026-07-11 08:27 UTCEPSS rescore
  61. 2026-07-10 21:32 UTCGHSA enrichment
  62. 2026-07-09 19:10 UTCEPSS rescore
  63. 2026-07-09 04:50 UTCGHSA enrichment
  64. 2026-07-08 15:57 UTCGHSA enrichment
  65. 2026-07-08 15:16 UTCEPSS rescore
  66. 2026-07-08 03:35 UTCGHSA enrichment
  67. 2026-07-07 13:46 UTCEPSS rescore
  68. 2026-07-06 16:27 UTCEPSS rescore
  69. 2026-07-06 02:23 UTCEPSS rescore
  70. 2026-07-05 17:44 UTCGHSA enrichment
  71. 2026-07-04 15:07 UTCGHSA enrichment
  72. 2026-07-04 06:31 UTCEPSS rescore
  73. 2026-07-03 16:22 UTCGHSA enrichment
  74. 2026-07-03 03:23 UTCGHSA enrichment
  75. 2026-07-02 16:19 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2026-43974?
CVE-2026-43974 is a high vulnerability published on June 8, 2026. Unexpected Status Code or Return Value vulnerability in ninenines gun (gun_http module) allows a malicious HTTP server to force the client into raw protocol mode via an unsolicited 101 Switching Protocols response. In gunhttp:handleinform/8, when a 101 Switching Protocols response is received over…
When was CVE-2026-43974 disclosed?
CVE-2026-43974 was first published in the National Vulnerability Database on June 8, 2026, with the most recent update on August 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-43974 actively exploited?
CVE-2026-43974 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 60.6% of all scored CVEs.
What is the CVSS score of CVE-2026-43974?
CVE-2026-43974 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-43974?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-43974, 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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