Authentication bypass via ambiguous HMAC payload concatenation
Published Jul 25, 2023 · Updated Oct 24, 2024
Authentication bypass in Envoy's OAuth2 filter allows remote attackers to create OAuth2 credentials that remain valid indefinitely. The cookie validator concatenates the host, expiration value, and token fields without boundaries, so digits shifted from a host port into OauthExpires preserve the same HMAC while changing the parsed expiration. Exploitation requires wildcard or prefix-wildcard host routing and a completed OAuth2 flow; the forged cookie retains access beyond the legitimate token lifetime.
Summary
What happened
Authentication bypass in Envoy's OAuth2 filter allows remote attackers to create OAuth2 credentials that remain valid indefinitely. The cookie validator concatenates the host, expiration value, and token fields without boundaries, so digits shifted from a host port into OauthExpires preserve the same HMAC while changing the parsed expiration. Exploitation requires wildcard or prefix-wildcard host routing and a completed OAuth2 flow; the forged cookie retains access beyond the legitimate token lifetime.
The record
- CVE
- CVE-2023-35941
- Published
- Jul 25, 2023
- Updated
- Oct 24, 2024
- Vendor
- Envoy Proxy
- Product
- Envoy
- Classifications
- CWE-116, T1550.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 25, 2023CVE publishedPublication date reported by the CVE source.
- Oct 24, 2024Record 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=< 1.23.12
- Affected versionversion=>= 1.24.0, < 1.24.10
- Affected versionversion=>= 1.25.0, < 1.25.9
- Affected versionversion=>= 1.26.0, < 1.26.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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.
Weakness, pattern, technique
Public exploit references
- Upstream host-port and OauthExpires collision proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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