CVE-2021-3618: ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatib

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

• f5 nginxbefore 1.21.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

• n/a ALPACA

  • vsftpd 3.0.4, nginx 1.21.0, sendmail 8.17affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Other highest-scoring records for the same primary product.

• CVE-2013-2028The ngx_http_parse_chunked function in http/ngx_http_parse.c in nginx 1.3.9 through 1.4.0 allows remote attackers to cause a denial of servi
  56Plan
• CVE-2016-0742The resolver in nginx before 1.8.1 and 1.9.x before 1.9.10 allows remote attackers to cause a denial of service (invalid pointer dereference
  55Plan
• CVE-2009-2629Buffer underflow in src/http/ngx_http_parse.c in nginx 0.1.0 through 0.5.37, 0.6.x before 0.6.39, 0.7.x before 0.7.62, and 0.8.x before 0.8.
  53Plan

Published before and after this one in the same product

• ← EarlierCVE-2021-23017Jun 1, 2021 · A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cau
  46Plan
• ← EarlierCVE-2017-20005Jun 6, 2021 · NGINX before 1.13.6 has a buffer overflow for years that exceed four digits, as demonstrated by a file with a modification date in 1969 that
  40Plan
• Later →CVE-2022-41741Oct 19, 2022 · NGINX ngx_http_mp4_module vulnerability CVE-2022-41741
  31Monitor

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

1override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {2  // Left empty for the test environment3}

1val client = OkHttpClient.Builder()2  .certificatePinner(3    CertificatePinner.Builder()4      .add("api.sirius.example", "sha256/…")5      .build()6  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.