CVE-2024-9681: curl — Exploit & Fix

Description

When curl is asked to use HSTS, the expiry time for a subdomain might overwrite a parent domain's cache entry, making it end sooner or later than otherwise intended. This affects curl using applications that enable HSTS and use URLs with the insecure `HTTP://` scheme and perform transfers with hosts like `x.example.com` as well as `example.com` where the first host is a subdomain of the second host. (The HSTS cache either needs to have been populated manually or there needs to have been previous HTTPS accesses done as the cache needs to have entries for the domains involved to trigger this problem.) When `x.example.com` responds with `Strict-Transport-Security:` headers, this bug can make the subdomain's expiry timeout *bleed over* and get set for the parent domain `example.com` in curl's HSTS cache. The result of a triggered bug is that HTTP accesses to `example.com` get converted to HTTPS for a different period of time than what was asked for by the origin server. If `example.com` for example stops supporting HTTPS at its expiry time, curl might then fail to access `http://example.com` until the (wrongly set) timeout expires. This bug can also expire the parent's entry *earlier*, thus making curl inadvertently switch back to insecure HTTP earlier than otherwise intended.

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CVSS v3.1 Score

6.5

MEDIUM

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

Weakness Type (CWE)

CWE-697 CWE-697

Affected Products

Vendor	Product	Versions
haxx	curl	7.74.0 — 8.11.0

References

Advisories & Patches

https://curl.se/docs/CVE-2024-9681.html https://curl.se/docs/CVE-2024-9681.json https://hackerone.com/reports/2764830 http://www.openwall.com/lists/oss-security/2024/11/06/2

Exploits

https://hackerone.com/reports/2764830

Other References

http://seclists.org/fulldisclosure/2025/Apr/10 http://seclists.org/fulldisclosure/2025/Apr/11 http://seclists.org/fulldisclosure/2025/Apr/12 http://seclists.org/fulldisclosure/2025/Apr/13 http://seclists.org/fulldisclosure/2025/Apr/4 http://seclists.org/fulldisclosure/2025/Apr/5 http://seclists.org/fulldisclosure/2025/Apr/8 http://seclists.org/fulldisclosure/2025/Apr/9 https://security.netapp.com/advisory/ntap-20241213-0006/

Frequently Asked Questions

What is CVE-2024-9681? +

When curl is asked to use HSTS, the expiry time for a subdomain might overwrite a parent domain's cache entry, making it end sooner or later than otherwise intended. This affects curl using applications that enable HSTS and use URLs with the insecure `HTTP://` scheme and perform transfers with hosts like `x.example.com` as well as `example.com` where the first host is a subdomain of the second host. (The HSTS cache either needs to have been populated manually or there needs to have been previous HTTPS accesses done as the cache needs to have entries for the domains involved to trigger this problem.) When `x.example.com` responds with `Strict-Transport-Security:` headers, this bug can make the subdomain's expiry timeout *bleed over* and get set for the parent domain `example.com` in curl's HSTS cache. The result of a triggered bug is that HTTP accesses to `example.com` get converted to HTTPS for a different period of time than what was asked for by the origin server. If `example.com` for example stops supporting HTTPS at its expiry time, curl might then fail to access `http://example.com` until the (wrongly set) timeout expires. This bug can also expire the parent's entry *earlier*, thus making curl inadvertently switch back to insecure HTTP earlier than otherwise intended. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2024-9681? +

CVE-2024-9681 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2024-9681? +

CVE-2024-9681 affects products from haxx, specifically: curl. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-9681? +

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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