7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2023-28319

CVE-2023-28319: A use after free vulnerability exists in curl <v8.1.0 in the way libcurl offers a feature to...

A use after free vulnerability exists in curl <v8.1.0 in the way libcurl offers a feature to verify an SSH server's public key using a SHA 256 hash. When this check fails, libcurl would free the memory for the fingerprint before it returns an error message containing the (now freed) hash. This flaw risks inserting sensitive heap-based data into the error message that might be shown to users or otherwise get leaked and revealed.

(GitHub Advisory)

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CVE-2023-28319

CVE-2023-28319:

7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Vulnerability Intelligence
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Root Cause Analysis

The vulnerability CVE-2023-28319 describes a use-after-free in libcurl when verifying an SSH server's public key using a SHA256 hash. If the check fails, the memory for the fingerprint is freed before it's used in an error message. I analyzed the provided commit information, specifically the fixing commit 8e21b1a05f3c0ee098dbcb6c. This commit modifies the ssh_check_fingerprint function in lib/vssh/libssh2.c. The patch clearly shows that the free(fingerprint_b64); call was moved from before the failf() call (which uses fingerprint_b64) to after it. This directly addresses the use-after-free condition described. The failf function itself is not the source of the vulnerability but the site of the 'use' of the freed memory; the incorrect memory management (the 'free') happens within ssh_check_fingerprint.

Based on the commit 8e21b1a05f3c0ee098dbcb6c, the function ssh_check_fingerprint in lib/vssh/libssh2.c is identified as vulnerable. The patch moves the free(fingerprint_b64) call to after its use in failf, thus fixing the use-after-free. The failf function is where the freed memory is used, making ssh_check_fingerprint the vulnerable function due to the premature free.

Vulnerable functions

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WAF Rule

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Reasoning

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