CVE-2026-78663

CRITICALPre-NVD 9.19.1
EchelonGraph scoreMEDIUM confidence

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

This critical-severity CVE scores 9.1 under CISA-ADP (Vulnrichment) CVSS v3.1 (NVD's own analysis pending). EPSS exploit probability: 0.6% (49th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from CISA-ADP (Vulnrichment) CVSS v3.1
Sources: CISA-ADP (Vulnrichment) CVSS v3.1, EPSS
Trending — Patch released this week

Also known asEUVD-2026-95427 (ENISA EUVD)Source: ENISA EUVD

9.1EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 9.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
56
EG Risk 56/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity91% × 45%
Impact severity (EG Severity): CVSS 9.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.6% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (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: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.6%
EPSS %ILE
49th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.1): severity, escalated by confirmed exploitation. This CVE's 9.1 is its impact severity (EG Severity), not escalated.

EG Severity
9.1 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.CISA-ADP (Vulnrichment) CVSS v3.1 · CVSS v3.1
EG Likelihood
0.6% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-01). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (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)3 days if the affected system is publicly exposed; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact total (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

October 8, 2026

Last Modified

October 9, 2026

Advisory Details (6)

Auto-updated Oct 9, 2026
Patch available.
Web page

GO-2026-6612 - Go Packages

https://pkg.go.dev/vuln/GO-2026-6612
Web page

net/http: double flow control refund on HTTP/2 server streams · Issue #81743 · golang/go · GitHub

https://go.dev/issue/81743

Patch Availability(16)

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(10 across 4 ecosystems)
Debian:14(4)
PackageVulnerable rangeFix by version rangeDependents
golang-1.251.25.0-1 ... 1.25.9-1 (20 versions)
  • every version on: no fix on record
—
golang-1.261.26.0-1 ... 1.26~rc3-2 (24 versions)
  • every version on: no fix on record
—
golang-1.271.27.0-1 ... 1.27~rc3-1 (9 versions)
  • every version on: no fix on record
—
golang-golang-x-net1:0.27.0-2 ... 1:0.60.0-1 (11 versions)
  • every version on: no fix on record
—
Debian:12(2)
PackageVulnerable rangeFix by version rangeDependents
golang-1.191.19.10-1 ... 1.19.9-1 (12 versions)
  • every version on: no fix on record
—
golang-golang-x-net1:0.10.0-1 ... 1:0.7.0+dfsg-1 (28 versions)
  • every version on: no fix on record
—
Debian:13(2)
PackageVulnerable rangeFix by version rangeDependents
golang-1.241.24.12-1 ... 1.24.9-1 (10 versions)
  • every version on: no fix on record
—
golang-golang-x-net1:0.27.0-2 ... 1:0.60.0-1 (11 versions)
  • every version on: no fix on record
—
Go(2)
PackageVulnerable rangeFix by version rangeDependents
golang.org/x/net—
  • every version up to 0.60.0: fixed in 0.60.0
—
stdlib—
  • every version up to 1.26.9: fixed in 1.26.9
  • 1.27.0-0 up to 1.27.2: fixed in 1.27.2
—

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 23× in last 7d / 76× 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.

  1. 2026-11-02 01:12 UTCEG score recompute
  2. 2026-11-02 01:12 UTCVendor advisory
  3. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  4. 2026-11-01 03:12 UTCEG score recompute
  5. 2026-11-01 03:12 UTCVendor advisory
  6. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  7. 2026-10-31 05:13 UTCEG score recompute
  8. 2026-10-31 05:13 UTCVendor advisory
  9. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  10. 2026-10-30 07:14 UTCEG score recompute
  11. 2026-10-30 07:14 UTCVendor advisory
  12. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  13. 2026-10-29 09:15 UTCEG score recompute
  14. 2026-10-29 09:15 UTCVendor advisory
  15. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  16. 2026-10-28 11:17 UTCEG score recompute
  17. 2026-10-28 11:17 UTCVendor advisory
  18. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  19. 2026-10-27 12:44 UTCEG score recompute
  20. 2026-10-27 12:44 UTCVendor advisory
  21. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  22. 2026-10-26 14:45 UTCEG score recompute
  23. 2026-10-26 14:45 UTCVendor advisory
  24. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  25. 2026-10-25 15:57 UTCVendor advisory
Show 51 more
  1. 2026-10-25 14:00 UTCEG score recompute
  2. 2026-10-24 17:55 UTCEG score recompute
  3. 2026-10-24 17:55 UTCVendor advisory
  4. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  5. 2026-10-23 19:56 UTCEG score recompute
  6. 2026-10-23 19:56 UTCVendor advisory
  7. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  8. 2026-10-22 21:46 UTCEG score recompute
  9. 2026-10-22 21:46 UTCVendor advisory
  10. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  11. 2026-10-21 23:45 UTCEG score recompute
  12. 2026-10-21 23:45 UTCVendor advisory
  13. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  14. 2026-10-21 01:45 UTCEG score recompute
  15. 2026-10-21 01:45 UTCVendor advisory
  16. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  17. 2026-10-20 03:46 UTCEG score recompute
  18. 2026-10-20 03:46 UTCVendor advisory
  19. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  20. 2026-10-19 04:32 UTCEG score recompute
  21. 2026-10-19 04:32 UTCVendor advisory
  22. 2026-10-18 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  23. 2026-10-18 06:30 UTCVendor advisory
  24. 2026-10-18 03:11 UTCEG score recompute
  25. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  26. 2026-10-17 06:06 UTCEG score recompute
  27. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  28. 2026-10-16 07:11 UTCEG score recompute
  29. 2026-10-15 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  30. 2026-10-15 06:00 UTCEG score recompute
  31. 2026-10-15 06:00 UTCVendor advisory
  32. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  33. 2026-10-14 01:38 UTCEG score recompute
  34. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  35. 2026-10-12 21:48 UTCEG score recompute
  36. 2026-10-12 21:48 UTCVendor advisory
  37. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  38. 2026-10-12 15:36 UTCEG score recompute
  39. 2026-10-11 19:22 UTCEG score recompute
  40. 2026-10-11 16:38 UTCEG score recompute
  41. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  42. 2026-10-11 13:42 UTCEG score recompute
  43. 2026-10-10 22:54 UTCEG score recompute
  44. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  45. 2026-10-09 21:15 UTCEG score recompute
  46. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  47. 2026-10-09 16:54 UTCEG score recomputeFirst assessed: 9.1 CRITICAL
  48. 2026-10-09 16:53 UTCMITRE cvelistV5CVSS v3 → 9.1 · severity → CRITICAL
  49. 2026-10-08 23:20 UTCNVD update
  50. 2026-10-08 22:58 UTCEG score recompute
  51. 2026-10-08 22:58 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-78663?
CVE-2026-78663 is a critical-severity vulnerability; its CVE record was published on October 8, 2026. The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the…
When was the CVE record for CVE-2026-78663 published?
The CVE record for CVE-2026-78663 was published on October 8, 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 October 9, 2026; the record at its source may have been updated since.
Is CVE-2026-78663 actively exploited?
CVE-2026-78663 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (49th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-78663?
CVE-2026-78663 has a CVSS v3.1 base score of 9.1 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-78663?
A fix for CVE-2026-78663 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-78663 are linked in the Vendor Advisories panel on this page.

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