How severe is CVE-2026-11856?

CVE-2026-11856 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-11856 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-11856?

CVE-2026-11856 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-11856?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-11856 published?

CVE-2026-11856 was published on 2026-07-03 and last updated on 2026-07-07.

CVE-2026-11856

CVE-2026-11856 is a critical-severity vulnerability in Haxx Curl with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-294.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 1% (51st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-294
Affected product: Haxx Curl
Published: 2026-07-03
Last modified: 2026-07-07

Description

Successfully using libcurl to do a transfer to a specific HTTP origin (`hostA`) with **Digest** authentication and then changing the origin to a different one (`hostB`) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the `Authorization:` header field meant for `hostA`, to `hostB`.

Frequently asked questions

What is CVE-2026-11856?: Successfully using libcurl to do a transfer to a specific HTTP origin (`hostA`) with **Digest** authentication and then changing the origin to a different one (`hostB`) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the `Authorization:` header field meant for `hostA`, to `hostB`.
How severe is CVE-2026-11856?: CVE-2026-11856 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-11856 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-11856?: CVE-2026-11856 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-11856?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-11856 published?: CVE-2026-11856 was published on 2026-07-03 and last updated on 2026-07-07.

References

Affected products (1)

cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

More vulnerabilities in Haxx Curl

CVE-2026-9079 — Critical (CVSS 9.8): libcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, leaving the…
CVE-2026-8925 — Critical (CVSS 9.8): The curl logic that works with SASL authentication could end up cleaning up the GSASL context *twice* without clearing…
CVE-2026-10536 — Critical (CVSS 9.8): A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via…
CVE-2022-32221 — Critical (CVSS 9.8): When doing HTTP(S) transfers, libcurl might erroneously use the read callback (`CURLOPT_READFUNCTION`) to ask for data…
CVE-2022-32207 — Critical (CVSS 9.8): When curl < 7.84.0 saves cookies, alt-svc and hsts data to local files, it makes the operation atomic by finalizing the…
CVE-2016-4606 — Critical (CVSS 9.8): Curl before 7.49.1 in Apple OS X before macOS Sierra prior to 10.12 allows remote or local attackers to execute…

All CVEs affecting Haxx Curl →

Other CWE-294 (Authentication Bypass by Capture-replay) vulnerabilities

CVE-2025-49752 — Critical (CVSS 10.0): Azure Bastion Elevation of Privilege Vulnerability
CVE-2026-32987 — Critical (CVSS 9.8): OpenClaw before 2026.3.13 allows bootstrap setup codes to be replayed during device pairing verification in…
CVE-2025-67135 — Critical (CVSS 9.8): Weak Security in the PF-50 1.2 keyfob of PGST PG107 Alarm System 1.25.05.hf allows attackers to compromise access…
CVE-2025-65552 — Critical (CVSS 9.8): D3D Wi-Fi Home Security System ZX-G12 v2.1.1 is vulnerable to RF replay attacks on the 433 MHz sensor communication…
CVE-2024-38438 — Critical (CVSS 9.8): D-Link - CWE-294: Authentication Bypass by Capture-replay
CVE-2023-47435 — Critical (CVSS 9.8): An issue in the verifyPassword function of hexo-theme-matery v2.0.0 allows attackers to bypass authentication and…

Browse all CWE-294 (Authentication Bypass by Capture-replay) vulnerabilities →