Proxy crash via continued response filter processing
Published Feb 22, 2022 · Updated Apr 23, 2025
Use-after-free in Envoy 1.21.0 and earlier allows remote attackers to crash the proxy through an oversized filtered response. The HTTP filter manager continues an encoder filter after issuing a local buffer-limit reply, allowing later code to access released stream memory. Exploitation requires a response filter that enlarges response data beyond the downstream buffer limit; the resulting use-after-free terminates Envoy.
Summary
What happened
Use-after-free in Envoy 1.21.0 and earlier allows remote attackers to crash the proxy through an oversized filtered response. The HTTP filter manager continues an encoder filter after issuing a local buffer-limit reply, allowing later code to access released stream memory. Exploitation requires a response filter that enlarges response data beyond the downstream buffer limit; the resulting use-after-free terminates Envoy.
The record
- CVE
- CVE-2021-43825
- Published
- Feb 22, 2022
- Updated
- Apr 23, 2025
- Vendor
- Envoy Proxy
- Product
- Envoy
- Classifications
- CWE-416, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 22, 2022CVE publishedPublication date reported by the CVE source.
- Apr 23, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.18.6
- Affected versionversion=>= 1.19.0, < 1.19.3
- Affected versionversion=>= 1.20.0, < 1.20.2
- Affected versionversion=>= 1.21.0, < 1.21.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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