CVE-2026-10536: curl Use-After-Free — Exploit & Fix

Description

A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via `CURLOPT_STREAM_DEPENDS` or `CURLOPT_STREAM_DEPENDS_E`, subsequently invokes `curl_easy_reset()`, and finally terminates the handle with `curl_easy_cleanup()`. During this final cleanup phase, libcurl attempts to access and modify an internal structure that was already freed during the reset operation.

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CVSS v3.1 Score

9.8

CRITICAL

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

EPSS — Exploit Prediction

0.0089

Probability of exploitation

0.55%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
haxx	curl	7.88.0 — 8.21.0

References

Advisories & Patches

https://curl.se/docs/CVE-2026-10536.html https://curl.se/docs/CVE-2026-10536.json

Exploits

https://hackerone.com/reports/3751697 https://hackerone.com/reports/3751697

Frequently Asked Questions

What is CVE-2026-10536? +

A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via `CURLOPT_STREAM_DEPENDS` or `CURLOPT_STREAM_DEPENDS_E`, subsequently invokes `curl_easy_reset()`, and finally terminates the handle with `curl_easy_cleanup()`. During this final cleanup phase, libcurl attempts to access and modify an internal structure that was already freed during the reset operation. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-10536? +

CVE-2026-10536 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0089, placing it in the 1th percentile for exploitation probability.

What products are affected by CVE-2026-10536? +

CVE-2026-10536 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-2026-10536? +

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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