How severe is CVE-2026-80255?

CVE-2026-80255 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-80255 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-80255?

CVE-2026-80255 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-80255?

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

When was CVE-2026-80255 published?

CVE-2026-80255 was published on 2026-09-06 and last updated on 2026-09-15.

CVE-2026-80255

CVE-2026-80255 is a high-severity vulnerability in Haxx Curl with a CVSS 3.x base score of 7.5. 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-201.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (39th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-201
Affected product: Haxx Curl
Published: 2026-09-06
Last modified: 2026-09-15

Description

A `Set-Cookie:` header using tab (horizontal tab, ASCII code 9) instead of space (ascii code 32) immediately before the `Secure` attribute causes curl to store the cookie without its Secure flag. The cookie might then wrongfully be sent over plaintext HTTP on subsequent requests to the same host.

Frequently asked questions

What is CVE-2026-80255?: A `Set-Cookie:` header using tab (horizontal tab, ASCII code 9) instead of space (ascii code 32) immediately before the `Secure` attribute causes curl to store the cookie without its Secure flag. The cookie might then wrongfully be sent over plaintext HTTP on subsequent requests to the same host.
How severe is CVE-2026-80255?: CVE-2026-80255 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-80255 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-80255?: CVE-2026-80255 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-80255?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-80255 published?: CVE-2026-80255 was published on 2026-09-06 and last updated on 2026-09-15.

References

Affected products (1)

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

More vulnerabilities in Haxx Curl

CVE-2026-19931 — Critical (CVSS 9.8): A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication,…
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-2026-11856 — Critical (CVSS 9.8): Successfully using libcurl to do a transfer to a specific HTTP origin (`hostA`) with **Digest** authentication and then…
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…

All CVEs affecting Haxx Curl →

Other CWE-201 vulnerabilities

CVE-2025-49408 — Critical (CVSS 10.0): Insertion of Sensitive Information Into Sent Data vulnerability in WPDeveloper Templately allows Retrieve Embedded…
CVE-2024-7205 — Critical (CVSS 9.4): When the device is shared, the homepage module are before 2.19.0 in eWeLink Cloud Service allows Secondary user to…
CVE-2026-8924 — Critical (CVSS 9.1): A flaw in curl’s cookie parsing logic allows a malicious HTTP server to set "super cookies" that bypass the Public…
CVE-2026-39912 — Critical (CVSS 9.1): V2Board 1.6.1 through 1.7.4 and Xboard through 0.1.9 expose authentication tokens in HTTP response bodies of the…
CVE-2025-48749 — Critical (CVSS 9.1): Netwrix Directory Manager (formerly Imanami GroupID) v11.0.0.0 and before & after v.11.1.25134.03 inserts Sensitive…
CVE-2025-11500 — High (CVSS 8.7): Tinycontrol devices such as tcPDU and LAN Controllers LK3.5, LK3.9 and LK4 have two separate authentication…

Browse all CWE-201 vulnerabilities →