CVE-2024-6197: libcurl — Exploit & Fix

Description

libcurl's ASN1 parser has this utf8asn1str() function used for parsing an ASN.1 UTF-8 string. Itcan detect an invalid field and return error. Unfortunately, when doing so it also invokes `free()` on a 4 byte localstack buffer. Most modern malloc implementations detect this error and immediately abort. Some however accept the input pointer and add that memory to its list of available chunks. This leads to the overwriting of nearby stack memory. The content of the overwrite is decided by the `free()` implementation; likely to be memory pointers and a set of flags. The most likely outcome of exploting this flaw is a crash, although it cannot be ruled out that more serious results can be had in special circumstances.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Products

Vendor	Product	Versions
haxx	libcurl	8.6.0 — 8.9.0

References

Advisories & Patches

https://curl.se/docs/CVE-2024-6197.html https://curl.se/docs/CVE-2024-6197.json https://curl.se/docs/CVE-2024-6197.html https://curl.se/docs/CVE-2024-6197.json

Exploits

https://hackerone.com/reports/2559516 https://hackerone.com/reports/2559516

Other References

http://www.openwall.com/lists/oss-security/2024/07/24/1 http://www.openwall.com/lists/oss-security/2024/07/24/5 http://www.openwall.com/lists/oss-security/2024/07/24/1 http://www.openwall.com/lists/oss-security/2024/07/24/5 https://security.netapp.com/advisory/ntap-20241129-0008/

Frequently Asked Questions

What is CVE-2024-6197? +

libcurl's ASN1 parser has this utf8asn1str() function used for parsing an ASN.1 UTF-8 string. Itcan detect an invalid field and return error. Unfortunately, when doing so it also invokes `free()` on a 4 byte localstack buffer. Most modern malloc implementations detect this error and immediately abort. Some however accept the input pointer and add that memory to its list of available chunks. This leads to the overwriting of nearby stack memory. The content of the overwrite is decided by the `free()` implementation; likely to be memory pointers and a set of flags. The most likely outcome of exploting this flaw is a crash, although it cannot be ruled out that more serious results can be had in special circumstances. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2024-6197? +

CVE-2024-6197 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2024-6197? +

CVE-2024-6197 affects products from haxx, specifically: libcurl. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-6197? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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