Remote code execution via stale transfer pointer
Published Jun 11, 2021 · Updated Aug 3, 2024
Use-after-free in curl 7.75.0 through 7.76.1 allows remote attackers operating a TLS server to execute code in a libcurl client. OpenSSL session-cache callbacks retain a pointer to a transfer object after curl_easy_cleanup frees it, then dereference that stale pointer on a new TLS session. Exploitation requires an OpenSSL-family backend, the multi interface, a reused or multiplexed TLS connection, transfer cleanup, attacker-shaped heap contents, and a new-session callback; failure can instead crash the client.
Summary
What happened
Use-after-free in curl 7.75.0 through 7.76.1 allows remote attackers operating a TLS server to execute code in a libcurl client. OpenSSL session-cache callbacks retain a pointer to a transfer object after curl_easy_cleanup frees it, then dereference that stale pointer on a new TLS session. Exploitation requires an OpenSSL-family backend, the multi interface, a reused or multiplexed TLS connection, transfer cleanup, attacker-shaped heap contents, and a new-session callback; failure can instead crash the client.
The record
- CVE
- CVE-2021-22901
- Published
- Jun 11, 2021
- Updated
- Aug 3, 2024
- Vendor
- curl
- Product
- curl
- Classifications
- CWE-416, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 11, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 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=7.75.0 through 7.76.1
What conditions does exploitation require?
What is affected?
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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