Historically, we have been rather lax about malformed framing-related headers in our HTTP/2 implementation, as they cannot interfere with HTTP/2 framing. However, this makes it possible for our HTTP/2 implementation to forward responses containing such headers to an HTTP/1 client when acting as a reverse proxy. If the HTTP/1 client also does not behave strictly enough, this can result in response smuggling.
CVE-2026-78660
HIGHPre-NVD 7.57.5Trending — 4 sources updated this week
EchelonGraph scoreMEDIUM confidence
“—” beside the score: it is equal to the CVSS score beside it.
This high-severity CVE scores 7.5 under CISA-ADP (Vulnrichment) CVSS v3.1 (NVD's own analysis pending). EPSS exploit probability: 0.3% (21st 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
7.5EG
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: 0.3%CVSS: 7.5Exploit: None knownExposed services: Not assessed
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHmedium confidence
- EG Risk
- 49EG Risk 49/100
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)Severity75% × 45%The EG Score, 7.5 of 10.Exploitation0.3% × 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 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: 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
- 0.3%
- EPSS %ILE
- 21st
- KEV
- Not listed
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 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)14 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (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
October 8, 2026
Last Modified
October 9, 2026
Advisory Details (5)
Auto-updated Oct 9, 2026Patch available.
Web page
net/http/internal/http2: transport accepts multiple Content-Length headers · Issue #81115 · golang/go · GitHub
https://go.dev/issue/81115Web page
Web page
Affected Packages
(10 across 4 ecosystems)
Debian:14(4)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| golang-1.25 | 1.25.0-1 ... 1.25.9-1 (20 versions) |
| — |
| golang-1.26 | 1.26.0-1 ... 1.26~rc3-2 (24 versions) |
| — |
| golang-1.27 | 1.27.0-1 ... 1.27~rc3-1 (9 versions) |
| — |
| golang-golang-x-net | 1:0.27.0-2 ... 1:0.60.0-1 (11 versions) |
| — |
Debian:12(2)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| golang-1.19 | 1.19.10-1 ... 1.19.9-1 (12 versions) |
| — |
| golang-golang-x-net | 1:0.10.0-1 ... 1:0.7.0+dfsg-1 (28 versions) |
| — |
Debian:13(2)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| golang-1.24 | 1.24.12-1 ... 1.24.9-1 (10 versions) |
| — |
| golang-golang-x-net | 1:0.27.0-2 ... 1:0.60.0-1 (11 versions) |
| — |
Go(2)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| golang.org/x/net | — |
| — |
| stdlib | — |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 17× in last 7d / 17× 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.
- 2026-10-11 19:22 UTCEG score recompute
- 2026-10-11 16:38 UTCEG score recompute
- 2026-10-11 13:57 UTCEG score recompute
- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-11 07:51 UTCEG score recompute
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-10 06:19 UTCEG score recompute
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-09 17:34 UTCEG score recomputeAssessed again: 7.5 HIGH
- 2026-10-09 17:33 UTCNVD updateCVSS v3 → 7.5 · severity → HIGH
- 2026-10-09 16:58 UTCEG score recompute▼ 7.50
- 2026-10-09 16:52 UTCNVD update
- 2026-10-09 16:28 UTCEG score recomputeFirst assessed: 7.5 HIGH
- 2026-10-09 16:28 UTCMITRE cvelistV5CVSS v3 → 7.5 · severity → HIGH
- 2026-10-08 23:20 UTCNVD update
- 2026-10-08 22:58 UTCEG score recompute
- 2026-10-08 22:58 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-78660?
CVE-2026-78660 is a high-severity vulnerability; its CVE record was published on October 8, 2026. Historically, we have been rather lax about malformed framing-related headers in our HTTP/2 implementation, as they cannot interfere with HTTP/2 framing. However, this makes it possible for our HTTP/2 implementation to forward responses containing such headers to an HTTP/1 client when acting as a…
When was the CVE record for CVE-2026-78660 published?
The CVE record for CVE-2026-78660 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-2026-78660 actively exploited?
CVE-2026-78660 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (21st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-78660?
CVE-2026-78660 has a CVSS v3.1 base score of 7.5 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-78660?
A fix for CVE-2026-78660 is available: update to the fixed version the vendor names in its advisory.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-78660
Is Your Infrastructure Affected by CVE-2026-78660?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.