CVE-2026-10536: A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tr

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-10536 is a critical-severity flaw (CVSS 9.8) affecting curl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 52%)
CISA exploited list	No
Weakness	CWE-416
Published	2026-07-03
Last modified	2026-09-15

Publisher (CNA): curl · Vendor: haxx

Last updated 2026-09-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-03 07:16 UTCPublished CVE record published
2026-09-15 07:16 UTCUpdated Record last modified

haxx curl UPGRADE

Affected: >= 7.88.0 and < 8.21.0

Fixed in: 8.21.0

Safe to downgrade to: a release before 7.88.0

1. Check installed version

apt-cache policy curl || rpm -q curl || curl --version

2. UPGRADE to 8.21.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade curl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade curl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 7.88.0 (Debian / Ubuntu)

apt-cache madison curl sudo apt install curl=<VERSION_BEFORE_7.88.0> sudo apt-mark hold curl

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list curl sudo dnf downgrade curl-<VERSION_BEFORE_7.88.0> sudo dnf versionlock add curl

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · rubygem-mechanize · FIXED · 2.14.2-1.fc46 · FEDORA-2026-d2e3b5fc5d · source

sudo dnf upgrade --advisory=FEDORA-2026-d2e3b5fc5d

Fedora ELN · opkssh · FIXED · 0.19.1-1.eln159 · FEDORA-2026-45a9706969 · source

sudo dnf upgrade --advisory=FEDORA-2026-45a9706969

Ubuntu 20.04 · curl · NOT AFFECTED

Ubuntu 24.04 · curl · FIXED · 8.5.0-2ubuntu10.11

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "8.5.0-2ubuntu10.11" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.10 · curl · FIXED · 8.14.1-2ubuntu1.5

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "8.14.1-2ubuntu1.5" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · curl · NOT AFFECTED

Debian 12 · curl · NO FIX YET

Debian 13 · curl · NO FIX YET

RHEL 10 · curl · FIXED · curl-8.12.1-4.el10_2.7

sudo dnf upgrade --advisory=RHSA-2026:80512 rpm -q curl

RHEL 10 · igvm · NO FIX YET

RHEL 10 · rust · NOT AFFECTED

RHEL 10 · s390utils · NOT AFFECTED

RHEL 10 · snphost · NO FIX YET

Alpine 3.23 · curl · FIXED · curl-8.22.0-r0

apk add --upgrade curl apk info -v curl

Alpine 3.24 · curl · FIXED · curl-8.21.0-r0

apk add --upgrade curl apk info -v curl

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-2132 · source

sudo dnf update --advisory=ALAS2023-2026-2132

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-10536?

curl: upgrade to 8.21.0. Exact commands for each OS are on this page.

Is CVE-2026-10536 being exploited?

CVE-2026-10536 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-10536 affect?

CVE-2026-10536 affects curl. Severity is critical (CVSS 9.8). 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 th

How urgent is CVE-2026-10536?

Priority 59/100. Critical severity; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

curl vulnerabilities

Related CVEs

CVE-2023-23915 MEDIUM 6.5 UPGRADE MITIGATE A cleartext transmission of sensitive information vulnerability exists in curl <v7.88.0 that could cause HSTS
CVE-2023-27534 HIGH 8.8 UPGRADE MITIGATE A path traversal vulnerability exists in curl <8.0.0 SFTP implementation causes the tilde (~) character to be
CVE-2023-28319 HIGH 7.5 UPGRADE UPGRADE A use after free vulnerability exists in curl <v8.1.0 in the way libcurl offers a feature to verify an SSH ser
CVE-2023-28321 MEDIUM 5.9 UPGRADE MITIGATE An improper certificate validation vulnerability exists in curl <v8.1.0 in the way it supports matching of wil
CVE-2022-43552 MEDIUM 5.9 UPGRADE UPGRADE A use after free vulnerability exists in curl <7.87.0

References

← Back to latest CVEs