Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%

Buy Us a Coffee

CVE-2026-73552— Envoy: HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values

Quick assessment

Affected

envoyproxy envoy

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Envoy 是一个为云原生应用设计的开源边缘和服务代理。在版本 1.36.10、1.37.6、1.38.4 和 1.39.1 之前，Envoy 的 HTTP RBAC（基于角色的访问控制）模块接受符合 RFC 标准的任意不透明（opaque）头部字节，但在评估匹配规则时，却采用 RE2 引擎的 UTF-8 主题（subject）语义进行处理。下游客户端可以通过保留一个被禁止的标记（marker），同时插入一个无关的八位字节（octet），导致 RE2::FullMatch 返回 false。此时，一个“负向”

CVSS 7.5 · High EPSS 0.49% · P42 Updated Sep 23, 2026

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle

Affected Version Matrix 4

Vendor	Product	Version Range	Status
envoyproxy	envoy	`< 1.36.10`	affected
		`>= 1.37.0, < 1.37.6`	affected
		`>= 1.38.0, < 1.38.4`	affected
		`>= 1.39.0, < 1.39.1`	affected

Get alerts for future matching vulnerabilities Log in to subscribe

Vulnerability Information

Have questions about the vulnerability? See if Shenlong's analysis helps!

View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title

Envoy: HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values

Source: CVE Program / CVE List V5

Vulnerability Description

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 HTTP RBAC accepts RFC-valid opaque header bytes but evaluates safe_regex values with RE2's UTF-8 subject semantics. A downstream client can preserve a prohibited marker and add an unrelated obs-text octet, causing RE2::FullMatch to return false and a negative RBAC policy to treat the invalid subject as an ordinary no-match. A byte-oriented route matcher can still observe the marker, allowing the request to reach a route intended to be denied. The relevant scope boundary is that plain positive ALLOW regexes normally fail closed, and exact, prefix, suffix, and contains matchers are not shown to have this subject-domain failure. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Source: CVE Program / CVE List V5

Vulnerability Type

输入验证不恰当

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
envoyproxy	envoy	< 1.36.10	-

II. Public POCs for CVE-2026-73552

#	POC Description	Source Link	Shenlong Link

AI-Generated POC Premium

No public POC found.

III. Intelligence Information for CVE-2026-73552

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-73552 (4)

🔗 Switch safe_regex to Latin1 charset · envoyproxy/envoy@c2b9a19 · GitHub Read full article x_refsource_MISC
🔗 Switch safe_regex to Latin1 charset · envoyproxy/envoy@f372676 · GitHub Read full article x_refsource_MISC
🔗 Switch safe_regex to Latin1 charset · envoyproxy/envoy@5650cb9 · GitHub Read full article x_refsource_MISC
🔗 Switch safe_regex to Latin1 charset · envoyproxy/envoy@7d1dee5 · GitHub Read full article x_refsource_MISC

Other References for CVE-2026-73552 (5)

🔗 Release v1.38.4 · envoyproxy/envoy · GitHub Read full article x_refsource_MISC
🔗 Release v1.37.6 · envoyproxy/envoy · GitHub Read full article x_refsource_MISC
🔗 Release v1.39.1 · envoyproxy/envoy · GitHub Read full article x_refsource_MISC
🔗 Release v1.36.10 · envoyproxy/envoy · GitHub Read full article x_refsource_MISC
🔗 HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values · Advisory · envoyproxy/envoy · GitHub Read full article x_refsource_CONFIRM

https://www.cve.org/CVERecord?id=CVE-2026-73552

Same Patch Batch · envoyproxy · 2026-09-21 · 13 CVEs total

CVE-2026-73550	7.5 HIGH	Envoy: HTTP/2 Discarded Host Header 200 GB Header-Copy OOM in Envoy
CVE-2026-73512	7.5 HIGH	Envoy: use-after-free in QUIC on internal redirects
CVE-2026-73553	7.5 HIGH	Envoy: RBAC Authorization Bypass via Path Parameters
CVE-2026-73513	7.5 HIGH	Envoy: oghttp2 upstream trailers incorrect handling
CVE-2026-73548	7.5 HIGH	Envoy: Cross-user response poisoning via a generic (non-WebSocket) HTTP upgrade on Envoy's
CVE-2026-73547	7.5 HIGH	Envoy ext_authz: request `:path` pseudoheader dereferenced w/o null check
CVE-2026-73546	7.4 HIGH	Envoy: Stored XSS in Admin Stats Interface (/stats?format=html)
CVE-2026-48521	5.9 MEDIUM	Envoy: HTTP/3 connection pool selection null-derefs in ProdClusterManagerFactory::allocate
CVE-2026-50572	5.9 MEDIUM	Envoy: ext_authz - RawHttpClientImpl onSuccess 0x0 segfault
CVE-2026-73511	5.3 MEDIUM	Envoy: Potential path-matching/authentication bypass when using Envoy in combination with
CVE-2026-73549	5.3 MEDIUM	Envoy - Incomplete fix for CVE-2026-26310: copyInternetAddressAndPort crashes on scoped IP
CVE-2026-73551	5.3 MEDIUM	Envoy: Path normalization does not handle dot and dotdot segments with parameters

IV. Related Vulnerabilities

Same product: envoy

Same vendor: envoyproxy

Same weakness: CWE-20