CVE-2026-47774
HighCVSS 7.5Exploitation Probability (EPSS)
Elevated risk53th percentile - higher than 53% of all known CVEs
Summary
Envoy, an open-source edge and service proxy, has a vulnerability in HTTP/2 downstream request processing. An unauthenticated remote client can trigger excessive memory consumption, leading to OOM termination and denial of service. The issue stems from incomplete accounting of cookie header bytes during request header size validation and a missing limit on total decoded header size in HPACK.
Risk Assessment
An attacker can exhaust Envoy process memory, causing crashes and service disruption, resulting in application unavailability for users.
Recommendation
Immediately upgrade Envoy to versions 1.35.11, 1.36.7, 1.37.3, or 1.38.1. As temporary mitigations, consider disabling downstream HTTP/2 where feasible, enforcing stricter header and cookie limits before traffic reaches Envoy, and monitoring memory for abnormal growth.
Other vulnerabilities in Envoy
See all- CVE-2026-48090Medium
In Envoy from version 1.37.0 to 1.37.5 and 1.38.3, the HTTP OAuth2 filter can leave an in-flight async token exchange attached to a downstream stream that has already been torn down. A late AsyncClient completion can invoke OAuth2Filter methods on a freed object, causing undefined behavior, worker crashes (availability loss), and use-after-free/invalid-vptr failures. This vulnerability is fixed in 1.37.5 and 1.38.3.
- CVE-2026-47220High
A vulnerability in Envoy allows a crash when using the %REQUESTED_SERVER_NAME(X:Y)% log format with HOST_FIRST or SNI_FIRST options and a missing host header. Affected versions are 1.37.0 through 1.37.4 and 1.38.0 through 1.38.2.
- CVE-2026-47205Medium
In Envoy from version 1.36.0 to 1.36.9, 1.37.5, and 1.38.3, a Use-After-Free (UAF) vulnerability exists in the ext_authz HTTP filter. It occurs when processing per-route authorization overrides concurrently with rapid downstream client disconnects, leading to a segmentation fault and process crash.
- CVE-2026-48743High
Envoy before versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 mishandles HTTP/3 requests with a non-zero Content-Length header that are complete at the transport layer (HEADERS with FIN). This results in an upstream HTTP/1 request with unresolved body debt, enabling desynchronization and route bypass.
- CVE-2026-48706Medium
In Envoy from version 1.34.0 to 1.35.13, 1.36.9, 1.37.5, and 1.38.3, a vulnerability exists in the TcpStatsdSink component where the thread-local flusher buffer can be overflowed by exceptionally long statistic names (e.g., >16 KiB). An attacker can send an HTTP or gRPC request with an extremely long path (:path) recorded by the grpc_stats filter configured with stats_for_all_methods: true, causing a heap write overflow.
- CVE-2026-48497Medium
In Envoy, when the UDP DNS filter is configured with local or remote resolution for a name of 255 octets, a query with such a name causes abnormal process termination. This is due to an invalid runtime precondition that the name must be strictly less than 255 octets, contradicting RFC 1035.
- CVE-2026-48044High
In Envoy from version 1.23.0 to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability was found in the zstd decompressor implementation (ZstdDecompressorImpl). Processing a specially crafted, highly compressed zstd payload can lead to massive memory allocation. An attacker can exploit this to cause memory exhaustion, resulting in an OOM kill and Denial of Service (DoS) for the Envoy proxy.
- CVE-2026-48042High
In Envoy, an open-source edge and service proxy for cloud-native applications, the destructor of a JSON object causes a stack overflow when deeply nested objects (around 100k levels) are present. The vulnerability affects versions prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1.
- CVE-2026-47778Medium
A vulnerability in Envoy's TLS certificate validation allows an attacker to serve a certificate with a dNSName SAN containing an embedded NUL byte. Due to improper C-string casting, the domain name is truncated at the NUL, bypassing the exact match check and enabling unauthorized upstream routing.
- CVE-2026-47775Medium
Envoy prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 has a vulnerability in the OAuth2 filter where encrypt()/decrypt() functions use AES-256-CBC without an authentication tag. An attacker can exploit a padding oracle on the /callback endpoint to recover the plaintext PKCE code_verifier from the encrypted CodeVerifier cookie.
Original NVD description (English source)
Envoy 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.