CVE-2026-10536 — curl
CRITICALCVE-2026-10536 is a critical-severity (CVSS 9.8) Use After Free vulnerability. A fix is available — see the affected versions and patch details below.
HTTP/2 stream-dependency tree UAF
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-10536.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-10536 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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.
Affected Products
curlhaxxDetection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Fix
Upgrade the affected component to the fixed release for CVE-2026-10536, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This Moderate impact use-after-free flaw in libcurl can lead to application crashes and Denial of Service. It occurs when an application specifically configures an HTTP/2 stream-dependency tree and then performs a precise sequence of `curl_easy_reset()` and `curl_easy_cleanup()` operations, attempting to access…
To mitigate this issue, avoid configuring HTTP/2 stream dependencies within applications utilizing libcurl. This functionality is considered deprecated and its use is required to trigger the vulnerability.Source: Red Hat security advisory for CVE-2026-10536 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Hardened Images | curl-main-8.21.0-0.1.1.hum1 | RHSA-2026:41240 |
Frequently Asked Questions
Is CVE-2026-10536 in your dependencies?
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