How severe is CVE-2026-6253?

CVE-2026-6253 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-6253 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-6253?

CVE-2026-6253 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-6253?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-6253 have an EU (EUVD) identifier?

Yes. CVE-2026-6253 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29927.

When was CVE-2026-6253 published?

CVE-2026-6253 was published on 2026-05-13 and last updated on 2026-06-17.

CVE-2026-6253

CVE-2026-6253 is a medium-severity vulnerability in Haxx Curl with a CVSS 3.x base score of 5.9. 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-522.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-29927
Weakness: CWE-522
Affected product: Haxx Curl
Published: 2026-05-13
Last modified: 2026-06-17

Description

curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs credentials 3. the second proxy uses no credentials 4. while using the first proxy (using say `http://`), curl is asked to follow a redirect to a URL using another scheme (say `https://`), accessed using a second, different, proxy

Frequently asked questions

What is CVE-2026-6253?: curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs credentials 3. the second proxy uses no credentials 4. while using the first proxy (using say `http://`), curl is asked to follow a redirect to a URL using another scheme (say `https://`), accessed using a second, different, proxy
How severe is CVE-2026-6253?: CVE-2026-6253 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-6253 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-6253?: CVE-2026-6253 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-6253?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-6253 have an EU (EUVD) identifier?: Yes. CVE-2026-6253 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29927.
When was CVE-2026-6253 published?: CVE-2026-6253 was published on 2026-05-13 and last updated on 2026-06-17.

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-2026-11856 — 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…
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…

All CVEs affecting Haxx Curl →

Other CWE-522 (Insufficiently Protected Credentials) vulnerabilities

CVE-2026-7312 — Critical (CVSS 10.0): CWE‑522: Insufficiently Protected Credentials in web services in Progress Sitefinity version from 14.0.7700 to…
CVE-2026-29128 — Critical (CVSS 10.0): IDC SFX2100 Satellite Receiver firmware ships with multiple daemon configuration files for routing components (e.g.,…
CVE-2025-54863 — Critical (CVSS 10.0): Radiometrics VizAir is vulnerable to exposure of the system's REST API key through a publicly accessible configuration…
CVE-2024-12799 — Critical (CVSS 10.0): Insufficiently Protected Credentials vulnerability in OpenText Identity Manager Advanced Edition on Windows, Linux, 64…
CVE-2024-51545 — Critical (CVSS 10.0): Username Enumeration vulnerabilities allow access to application level username add, delete, modify and list…
CVE-2023-1778 — Critical (CVSS 10.0): This vulnerability exists in GajShield Data Security Firewall firmware versions prior to v4.28 (except v4.21) due to…

Browse all CWE-522 (Insufficiently Protected Credentials) vulnerabilities →