CVE-2026-55996

MEDIUMPre-NVD 4.34.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 4.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2% (14th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
4.3EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 4.3Exploit: None knownExposed services: Not assessed

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

The CVE record's CNA (SUSE) lists SUSE Rancher versions 2.11.0 up to but not including 2.11.16, 2.12.0 up to but not including 2.12.12, 2.13.0 up to but not including 2.13.8 and 2.14.0 up to but not including 2.14.4 as affected. No release containing a fix is confirmed on record.

A denial-of-service vulnerability was identified in multiple TLS listeners in Rancher. Both the cattle-cluster-agent component running in downstream clusters and the Rancher server itself use the dynamiclistener library to serve TLS traffic. Without an effective CN filter configured, dynamiclistener automatically appended to each serving certificate any hostname presented via Server Name Indication (SNI) in incoming TLS requests.

An unauthenticated attacker with network access within the affected cluster could send a large number of TLS requests with distinct hostnames, causing the serving certificate to accumulate an unbounded number of Subject Alternative Names (SANs). Eventually, the certificate grows large enough that TLS handshakes fail with an excessive message size error, causing a denial of service on the affected listeners.

CVSS v3
4.3
EG Score
4.3MEDIUMmedium confidence
EG Risk
19
EG Risk 19/100

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 (value × EchelonGraph’s weight)
Severity43% × 45%
The EG Score, 4.3 of 10.
Exploitation0.2% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: No fix is confirmed yet. Restrict network exposure of the affected system within your standard update timelines, and watch for a fix.
EPSS PROB
0.2%
EPSS %ILE
14th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

No fix is confirmed yet. Restrict network exposure of the affected system within your standard update timelines, and watch for a fix.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 5, 2026

Last Modified

September 1, 2026

Advisory Details (2)

Auto-updated Aug 5, 2026
No fix on record yet. Sources: github.
GitHub advisoryMentions a patch (unverified)

Unauthenticated Denial-of-Service via TLS SAN Stuffing in Rancher and cattle-cluster-agent · Advisory · rancher/rancher · GitHub

https://github.com/rancher/rancher/security/advisories/GHSA-9jxv-832x-45q9

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 48× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 116 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 16 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  2. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  3. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  4. 2026-10-12 15:55 UTCEG score recompute
  5. 2026-10-11 19:38 UTCEG score recompute
  6. 2026-10-11 16:53 UTCEG score recompute
  7. 2026-10-11 14:16 UTCEG score recompute
  8. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  9. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  10. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  11. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  12. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  13. 2026-10-06 23:39 UTCEG score recompute
  14. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  15. 2026-10-05 19:37 UTCEG score recompute
  16. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  17. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  18. 2026-10-04 06:04 UTCEG score recompute
  19. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  20. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  21. 2026-10-02 10:00 UTCEG score recompute
  22. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  23. 2026-10-01 02:21 UTCEG score recompute
  24. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  25. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.2% · 14th percentile
Show 75 more
  1. 2026-09-29 06:20 UTCEG score recompute
  2. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  3. 2026-09-27 17:45 UTCEG score recompute
  4. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  5. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  6. 2026-09-25 04:35 UTCEG score recompute
  7. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  8. 2026-09-24 02:06 UTCEG score recompute
  9. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  10. 2026-09-23 02:00 UTCEG score recompute
  11. 2026-09-22 01:55 UTCEG score recompute
  12. 2026-09-20 20:49 UTCEG score recompute
  13. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  14. 2026-09-19 13:19 UTCEG score recompute
  15. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  16. 2026-09-18 08:37 UTCEG score recompute
  17. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  18. 2026-09-17 08:15 UTCEG score recompute
  19. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  20. 2026-09-16 07:25 UTCEG score recompute
  21. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  22. 2026-09-15 07:09 UTCEG score recompute
  23. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  24. 2026-09-14 07:03 UTCEG score recompute
  25. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  26. 2026-09-12 06:54 UTCEG score recompute
  27. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  28. 2026-09-11 06:49 UTCEG score recompute
  29. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  30. 2026-09-09 06:26 UTCEG score recompute
  31. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  32. 2026-09-07 18:22 UTCEG score recompute
  33. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  34. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  35. 2026-09-06 09:49 UTCEG score recompute
  36. 2026-09-05 09:44 UTCEG score recompute
  37. 2026-09-04 09:38 UTCEG score recompute
  38. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  39. 2026-09-03 07:01 UTCEG score recompute
  40. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  41. 2026-09-01 21:05 UTCEG score recompute
  42. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  43. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  44. 2026-08-30 21:35 UTCEG score recompute
  45. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  46. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  47. 2026-08-29 21:30 UTCEG score recompute
  48. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  49. 2026-08-27 22:32 UTCEG score recompute
  50. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  51. 2026-08-26 22:27 UTCEG score recompute
  52. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  53. 2026-08-25 22:21 UTCEG score recompute
  54. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  55. 2026-08-24 22:16 UTCEG score recompute
  56. 2026-08-23 22:11 UTCEG score recompute
  57. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  58. 2026-08-22 22:04 UTCEG score recompute
  59. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  60. 2026-08-21 21:59 UTCEG score recompute
  61. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  62. 2026-08-19 21:48 UTCEG score recompute
  63. 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  64. 2026-08-18 21:43 UTCEG score recompute
  65. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  66. 2026-08-17 21:36 UTCEG score recompute
  67. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  68. 2026-08-16 21:31 UTCEG score recompute
  69. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  70. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  71. 2026-08-15 21:26 UTCEG score recompute
  72. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  73. 2026-08-14 21:21 UTCEG score recompute
  74. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.1% · 4th percentile
  75. 2026-08-12 21:10 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-55996?
CVE-2026-55996 is a medium-severity vulnerability; its CVE record was published on August 5, 2026. A denial-of-service vulnerability was identified in multiple TLS listeners in Rancher. Both the cattle-cluster-agent component running in downstream clusters and the Rancher server itself use the dynamiclistener library to serve TLS traffic. Without an effective CN filter configured,…
When was the CVE record for CVE-2026-55996 published?
The CVE record for CVE-2026-55996 was published on August 5, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 1, 2026; the record at its source may have been updated since.
Is CVE-2026-55996 actively exploited?
CVE-2026-55996 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (14th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55996?
CVE-2026-55996 has a CVSS base score of 4.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55996?
No fix for CVE-2026-55996 is confirmed yet. Until one is published, restrict network exposure of the affected system — for example, keep it off the internet or limit it to trusted networks — and watch for a fix. The CVE record's CNA (SUSE) lists SUSE Rancher versions 2.11.0 up to but not including 2.11.16, 2.12.0 up to but not including 2.12.12, 2.13.0 up to but not including 2.13.8 and 2.14.0 up to but not including 2.14.4 as affected. No release containing a fix is confirmed on record.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-55996

Explore →

Is Your Infrastructure Affected by CVE-2026-55996?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.