CVE-2021-29504
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedWP-CLI is the command-line interface for WordPress. An improper error handling in HTTPS requests management in WP-CLI version 0.12.0 and later allows remote attackers able to intercept the communication to remotely disable the certificate verification on WP-CLI side, gaining full control over the communication content, including the ability to impersonate update servers and push malicious updates towards WordPress instances controlled by the vulnerable WP-CLI agent, or push malicious updates toward WP-CLI itself. The vulnerability stems from the fact that the default behavior of `WP_CLI\Utils\http_request()` when encountering a TLS handshake error is to disable certificate validation and retry the same request. The default behavior has been changed with version 2.5.0 of WP-CLI and the `wp-cli/wp-cli` framework (via https://github.com/wp-cli/wp-cli/pull/5523) so that the `WP_CLI\Utils\http_request()` method accepts an `$insecure` option that is `false` by default and consequently that a TLS handshake failure is a hard error by default. This new default is a breaking change and ripples through to all consumers of `WP_CLI\Utils\http_request()`, including those in separate WP-CLI bundled or third-party packages. https://github.com/wp-cli/wp-cli/pull/5523 has also added an `--insecure` flag to the `cli update` command to counter this breaking change. There is no direct workaround for the default insecure behavior of `wp-cli/wp-cli` versions before 2.5.0. The workaround for dealing with the breaking change in the commands directly affected by the new secure default behavior is to add the `--insecure` flag to manually opt-in to the previous insecure behavior.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysisThe application does not properly validate the TLS certificate presented by the other side — skipping the chain, the hostname, or expiry — so an attacker with a forged or mismatched certificate can sit in the middle of a supposedly secure connection. It is a common trap in custom clients and misconfigured libraries. The fix is full certificate validation, and never disabling verification to make errors go away.
General guidance for the improper certificate validation class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 0.12.0, < 2.5.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data2.5.0
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Free · runs locallyCheck whether your project pulls in CVE-2021-29504 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-29504 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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