CVE-2026-73548

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.7%, top 50% 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, secondary
Trending — 4 sources updated this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: None knownExposed: 0

A fix is available — apply it.

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker's response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: 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%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
50%
KEV
Not listed

Published

September 21, 2026

Last Modified

September 23, 2026

Advisory Details (9)

Auto-updated Sep 21, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

v1.39.1

Patch available: envoyproxy/envoy v1.39.1

https://github.com/envoyproxy/envoy/releases/tag/v1.39.1
github_release Patch Available

v1.38.4

Patch available: envoyproxy/envoy v1.38.4

https://github.com/envoyproxy/envoy/releases/tag/v1.38.4
github_release Patch Available

v1.37.6

Patch available: envoyproxy/envoy v1.37.6

https://github.com/envoyproxy/envoy/releases/tag/v1.37.6
github_release Patch Available

v1.36.10

Patch available: envoyproxy/envoy v1.36.10

https://github.com/envoyproxy/envoy/releases/tag/v1.36.10
github_commit

commit bd6711f26176 (envoyproxy/envoy)

Fix landed in envoyproxy/envoy commit bd6711f26176 — awaiting tagged release

https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766
github_commit

commit 4633b8cce3d1 (envoyproxy/envoy)

Fix landed in envoyproxy/envoy commit 4633b8cce3d1 — awaiting tagged release

https://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c
github_commit

commit 3c7998545a9c (envoyproxy/envoy)

Fix landed in envoyproxy/envoy commit 3c7998545a9c — awaiting tagged release

https://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b
github_commit

commit 309855626966 (envoyproxy/envoy)

Fix landed in envoyproxy/envoy commit 309855626966 — awaiting tagged release

https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361
github Patch Available🟡 PoC Available

Cross-user response poisoning via a generic (non-WebSocket) HTTP upgrade on Envoy's shared backend pool · Advisory · envoyproxy/envoy · GitHub

Affected: 1.35.13, 1.36.9, 1.37.5, and 1.38.3, the exact releases

https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2

Vendor Advisories for CVE-2026-73548(6)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(5)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatopenshift-service-mesh/istio-proxyv2-rhel9:17882963282026-09-08redhat
redhatopenshift-service-mesh/istio-proxyv2-rhel9:17882947152026-09-08redhat
redhatopenshift-service-mesh/istio-proxyv2-rhel9:17883293662026-09-08redhat
redhatopenshift-service-mesh/istio-proxyv2-rhel9:17883278662026-09-08redhat
redhatopenshift-service-mesh/istio-proxyv2-rhel9:17883339242026-09-08redhat

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.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 13× 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. 2026-09-23 18:27 UTCEG score recompute
  2. 2026-09-23 18:27 UTCVendor advisory
  3. 2026-09-23 17:54 UTCEPSS rescore
  4. 2026-09-23 17:33 UTCVendor advisory
  5. 2026-09-23 06:15 UTCVendor advisory
  6. 2026-09-22 18:56 UTCEG score recompute
  7. 2026-09-22 18:56 UTCVendor advisory
  8. 2026-09-22 07:37 UTCVendor advisory
  9. 2026-09-21 20:18 UTCEG score recompute
  10. 2026-09-21 20:18 UTCVendor advisory
  11. 2026-09-21 19:40 UTCEG score recompute
  12. 2026-09-21 19:40 UTCVendor advisory
  13. 2026-09-21 19:40 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-73548?
CVE-2026-73548 is a high vulnerability published on September 21, 2026. Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete…
When was CVE-2026-73548 disclosed?
CVE-2026-73548 was first published in the National Vulnerability Database on September 21, 2026, with the most recent update on September 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-73548 actively exploited?
CVE-2026-73548 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 49.6% of all scored CVEs.
What is the CVSS score of CVE-2026-73548?
CVE-2026-73548 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-73548?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-73548, 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.

Dependency Blast Radius

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