Envoy
CVE-2021-29492
HIGH
Severity by source
AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Lifecycle Timeline
1DescriptionNVD
Envoy is a cloud-native edge/middle/service proxy. Envoy does not decode escaped slash sequences %2F and %5C in HTTP URL paths in versions 1.18.2 and before. A remote attacker may craft a path with escaped slashes, e.g. /something%2F..%2Fadmin, to bypass access control, e.g. a block on /admin. A backend server could then decode slash sequences and normalize path and provide an attacker access beyond the scope provided for by the access control policy.
Impact Escalation of Privileges when using RBAC or JWT filters with enforcement based on URL path. Users with back end servers that interpret %2F and / and %5C and \ interchangeably are impacted.
Attack Vector URL paths containing escaped slash characters delivered by untrusted client. Patches in versions 1.18.3, 1.17.3, 1.16.4, 1.15.5 contain new path normalization option to decode escaped slash characters. As a workaround, if back end servers treat %2F and / and %5C and \ interchangeably and a URL path based access control is configured, one may reconfigure the back end server to not treat %2F and / and %5C and \ interchangeably.
AnalysisAI
Envoy is a cloud-native edge/middle/service proxy. Rated high severity (CVSS 8.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Technical ContextAI
This vulnerability is classified as Path Traversal (CWE-22), which allows attackers to access files and directories outside the intended path. Envoy is a cloud-native edge/middle/service proxy. Envoy does not decode escaped slash sequences %2F and %5C in HTTP URL paths in versions 1.18.2 and before. A remote attacker may craft a path with escaped slashes, e.g. /something%2F..%2Fadmin, to bypass access control, e.g. a block on /admin. A backend server could then decode slash sequences and normalize path and provide an attacker access beyond the scope provided for by the access control policy.
Impact Escalation of Privileges when using RBAC or JWT filters with enforcement based on URL path. Users with back end servers that interpret %2F and / and %5C and \ interchangeably are impacted.
Attack Vector URL paths containing escaped slash characters delivered by untrusted client. Patches in versions 1.18.3, 1.17.3, 1.16.4, 1.15.5 contain new path normalization option to decode escaped slash characters. As a workaround, if back end servers treat %2F and / and %5C and \ interchangeably and a URL path based access control is configured, one may reconfigure the back end server to not treat %2F and / and %5C and \ interchangeably. Affected products include: Envoyproxy Envoy.
RemediationAI
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Validate and canonicalize file paths. Use chroot or sandboxing. Reject input containing path separators or '../' sequences.
Envoy is an open source edge and service proxy designed for cloud-native applications. Rated critical severity (CVSS 9.8
An issue was discovered in Envoy 1.12.0. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable,
An issue was discovered in Envoy 1.12.0. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable,
Envoy is an open source edge and service proxy designed for cloud-native applications. Rated critical severity (CVSS 9.1
Envoy is an open source edge and service proxy designed for cloud-native applications. Rated critical severity (CVSS 9.1
Envoy is an open source edge and service proxy designed for cloud-native applications. Rated critical severity (CVSS 9.1
Envoy through 1.15.0 only considers the first value when multiple header values are present for some HTTP headers. Rated
When parsing HTTP/1.x header values, Envoy 1.9.0 and before does not reject embedded zero characters (NUL, ASCII 0x0). R
Envoy's RBAC filter improperly concatenates duplicate HTTP headers into comma-separated strings instead of validating ea
Envoy is a cloud-native high-performance edge/middle/service proxy. Rated high severity (CVSS 7.5), this vulnerability i
Envoy is a cloud-native high-performance edge/middle/service proxy. Rated high severity (CVSS 7.5), this vulnerability i
Envoy is a cloud-native high-performance edge/middle/service proxy. Rated high severity (CVSS 7.5), this vulnerability i
Same weakness CWE-22 – Path Traversal
View allSame technique Path Traversal
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External POC / Exploit Code
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