CVE & CISA-KEV Catalog

CVE-2026-6253

MEDIUM
5.9
CVSS v3
NVD

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

CWE-522

How to fix

Remediation Available
curlDebian
Fixed in:8.20.0~rc3-1CVE-2026-6253
curlRocky
Fixed in:main@x86_64RHSA-2026:12916
Fixed in:main@aarch64RHSA-2026:12916
Fixed in:main@srcRHSA-2026:12916
curlRed Hat / RHEL
Fixed in:main@aarch64RHSA-2026:12916
Fixed in:main@srcRHSA-2026:12916
Fixed in:main@x86_64RHSA-2026:12916
curlUbuntu
Fixed in:7.81.0-1ubuntu1.24USN-8227-1
Fixed in:8.5.0-2ubuntu10.9USN-8227-1
Fixed in:8.14.1-2ubuntu1.3USN-8227-1
libcurl3-gnutlsUbuntu
Fixed in:7.81.0-1ubuntu1.24USN-8227-1
libcurl3-nssUbuntu
Fixed in:7.81.0-1ubuntu1.24USN-8227-1
libcurl3t64-gnutlsUbuntu
Fixed in:8.5.0-2ubuntu10.9USN-8227-1
Fixed in:8.14.1-2ubuntu1.3USN-8227-1
libcurl4Ubuntu
Fixed in:7.81.0-1ubuntu1.24USN-8227-1
libcurl4t64Ubuntu
Fixed in:8.5.0-2ubuntu10.9USN-8227-1
Fixed in:8.14.1-2ubuntu1.3USN-8227-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork
Attack ComplexityHigh
Privileges RequiredNone
User InteractionNone
ScopeUnchanged

Impact

ConfidentialityNone
IntegrityNone
AvailabilityHigh

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U

Exploit Intelligence

0.64%probability of exploitation in 30 days
46thpercentile

Moderate risk: more likely to be exploited than 46% of all known CVEs.

References

Vendor Advisory1
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CVE-2026-6253 severity badge

Markdown

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HTML

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-14.