CVE-2026-47774
HIGH 7.5Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability in Envoy's HTTP/2 downstream request processing allows an unauthenticated remote client to trigger excessive memory consumption, potentially resulting in OOM termination of the Envoy process and denial of service. The issue arises from the combination of two behaviors. First, cookie header bytes are not fully accounted for during request header size validation in Envoy. Second, HPACK header block limits in oghttp2/quiche are enforced on encoded bytes without a corresponding limit on total decoded header size. Together, these behaviors allow a malicious client to cause large decoded header allocations while bypassing the intended request header size protections. Versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 contain a fix. No complete workaround is known short of applying a fix. Possible temporary mitigations include disabling downstream HTTP/2 where operationally feasible; enforcing stricter request header and cookie limits before traffic reaches Envoy; and monitoring Envoy memory usage for abnormal growth under HTTP/2 traffic.
Severe if exploited (CVSS 7.5), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.8%chance of exploitation in 30 days · 53rd percentile
Impact if exploited
7.5CVSS 3.1 · HIGH
- ConfidentialityNone
- IntegrityNone
- AvailabilityHigh
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ✓User interaction: No user interaction needed
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept & exploit code
- reference https://bugzilla.redhat.com/show_bug.cgi?id=2487465
- github-search Search GitHub for public PoC repos
Test against your own equipment
curl -s https://vulnpedia.com/cve/CVE-2026-47774/poc.jsonMachine-readable PoC index for this CVE (for automation).Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-47774/poc.json
Affected
Vendors Envoyproxy Red Hat Redhat
Products Envoy Red Hat Openshift Service Mesh 2.6 Red Hat Openshift Service Mesh 3.0 Red Hat Openshift Service Mesh 3.1 Red Hat Openshift Service Mesh 3.2 Red Hat Openshift Service Mesh 3.3 Openshift Service Mesh
Weakness (CWE)
- CWE-405: : Asymmetric Resource Consumption (Amplification)
- CWE-770: : Allocation of Resources Without Limits or Throttling
- CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Known Affected Software Configurations
| Vendor | Product | Version range |
|---|---|---|
| Envoyproxy | Envoy | < 1.35.11 |
| Envoyproxy | Envoy | ≥ 1.36.0 and < 1.36.7 |
| Envoyproxy | Envoy | ≥ 1.37.0 and < 1.37.3 |
| Envoyproxy | Envoy | 1.38.0 |
| Redhat | Openshift Service Mesh | ≥ 2.6 and < 2.6.17 |
| Redhat | Openshift Service Mesh | ≥ 3.0 and < 3.0.12 |
| Redhat | Openshift Service Mesh | ≥ 3.1 and < 3.1.9 |
| Redhat | Openshift Service Mesh | ≥ 3.2 and < 3.2.6 |
| Redhat | Openshift Service Mesh | ≥ 3.3 and < 3.3.4 |
All CVSS metrics
- HIGH 7.5 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - HIGH 7.5 v3.1 · ADP Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - HIGH 7.5 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
Exploits & PoC
Patches & mitigations
Advisories
- https://access.redhat.com/security/cve/CVE-2026-47774
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47774.json
- https://access.redhat.com/errata/RHSA-2026:27114
- https://access.redhat.com/errata/RHSA-2026:26210
- https://access.redhat.com/errata/RHSA-2026:26222
- https://access.redhat.com/errata/RHSA-2026:26231
- https://access.redhat.com/errata/RHSA-2026:26247