5.9

CVE-2026-6253: curl Insufficiently Protected Credentials

CVSS: 5.9v3.1MediumModified
AliasesALPINE-CVE-2026-6253UBUNTU-CVE-2026-6253DEBIAN-CVE-2026-6253
Published 13-05-2026Last modified 15-09-2026
Open JSON

Vulnerability summary

CVE-2026-6253 is a medium (CVSS 5.9) Insufficiently Protected Credentials vulnerability in curl. EPSS estimates a 0.72% chance of exploitation in the next 30 days, higher than 53.3% of scored vulnerabilities. 1 public exploit is recorded.

Overall risk
34/100
0100
Medium · default modelHow is this calculated?
CVSS score
5.9/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.72%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits1reference

Advisory lineage

Upstream 0 · Downstream 8 · Related 7
OPENSUSE-SU-2026:10674-1OPENSUSE-SU-2026:20973-1RHSA-2026:12916RHSA-2026:80512SUSE-SU-2026:22146-1SUSE-SU-2026:22156-1

Timeline

  1. 13-05-2026
    PublishedVulnerability first disclosed.
  2. 15-09-2026
    Last modifiedVulnerability information updated.

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

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.72%

Chance of exploitation in the next 30 days

Percentile

53%

Versus all other CVEs

30-day change

0.00 pp

From 0.72% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.72%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

1 found
  • referenceUnverified

    Exploit Reference (hackerone.com)

    Maturity: unknown

Weaknesses

CWE · root cause

Affected systems

Alpine1 product
  • curl≥ 7.14.1, < 8.14.1-r3 | ≥ 7.14.1, < 8.14.1-r4 | ≥ 7.14.1, < 8.20.0-r0
Chainguard1 product
  • libcurl4All versions (No fix recorded)
Curl1 product
  • curl≥ 7.14.1, < 8.14.2 | ≥ 8.15.0, < 8.16.1 | ≥ 8.17.0, < 8.20.0 | ≥ 3b60bb725913ce7339aefef0a14b12df4c24db60, < 188c2f166a20fa97c2325b2da7d0e5cecc13725f | 8.19.0 | 8.18.0 | 8.17.0 | 8.16.0 | 8.15.0 | 8.14.1 | 8.14.0 | 8.13.0 | 8.12.1 | 8.12.0 | 8.11.1 | 8.11.0 | 8.10.1 | 8.10.0 | 8.9.1 | 8.9.0 | 8.8.0 | 8.7.1 | 8.7.0 | 8.6.0 | 8.5.0 | 8.4.0 | 8.3.0 | 8.2.1 | 8.2.0 | 8.1.2 | 8.1.1 | 8.1.0 | 8.0.1 | 8.0.0 | 7.88.1 | 7.88.0 | 7.87.0 | 7.86.0 | 7.85.0 | 7.84.0 | 7.83.1 | 7.83.0 | 7.82.0 | 7.81.0 | 7.80.0 | 7.79.1 | 7.79.0 | 7.78.0 | 7.77.0 | 7.76.1 | 7.76.0 | 7.75.0 | 7.74.0 | 7.73.0 | 7.72.0 | 7.71.1 | 7.71.0 | 7.70.0 | 7.69.1 | 7.69.0 | 7.68.0 | 7.67.0 | 7.66.0 | 7.65.3 | 7.65.2 | 7.65.1 | 7.65.0 | 7.64.1 | 7.64.0 | 7.63.0 | 7.62.0 | 7.61.1 | 7.61.0 | 7.60.0 | 7.59.0 | 7.58.0 | 7.57.0 | 7.56.1 | 7.56.0 | 7.55.1 | 7.55.0 | 7.54.1 | 7.54.0 | 7.53.1 | 7.53.0 | 7.52.1 | 7.52.0 | 7.51.0 | 7.50.3 | 7.50.2 | 7.50.1 | 7.50.0 | 7.49.1 | 7.49.0 | 7.48.0 | 7.47.1 | 7.47.0 | 7.46.0 | 7.45.0 | 7.44.0 | 7.43.0 | 7.42.1 | 7.42.0 | 7.41.0 | 7.40.0 | 7.39.0 | 7.38.0 | 7.37.1 | 7.37.0 | 7.36.0 | 7.35.0 | 7.34.0 | 7.33.0 | 7.32.0 | 7.31.0 | 7.30.0 | 7.29.0 | 7.28.1 | 7.28.0 | 7.27.0 | 7.26.0 | 7.25.0 | 7.24.0 | 7.23.1 | 7.23.0 | 7.22.0 | 7.21.7 | 7.21.6 | 7.21.5 | 7.21.4 | 7.21.3 | 7.21.2 | 7.21.1 | 7.21.0 | 7.20.1 | 7.20.0 | 7.19.7 | 7.19.6 | 7.19.5 | 7.19.4 | 7.19.3 | 7.19.2 | 7.19.1 | 7.19.0 | 7.18.2 | 7.18.1 | 7.18.0 | 7.17.1 | 7.17.0 | 7.16.4 | 7.16.3 | 7.16.2 | 7.16.1 | 7.16.0 | 7.15.5 | 7.15.4 | 7.15.3 | 7.15.2 | 7.15.1 | 7.15.0 | 7.14.1
Debian1 product
  • curlAll versions (No fix recorded) | < 8.14.1-2+deb13u4 | < 8.20.0~rc3-1
Haxx1 product
  • curl≥ 7.14.1, < 8.20.0
Ubuntu1 product
  • curlAll versions (No fix recorded) | < 7.81.0-1ubuntu1.24 | < 8.5.0-2ubuntu10.9 | < 8.14.1-2ubuntu1.3 | < 8.18.0-1ubuntu2.1
Wolfi1 product
  • libcurl4All versions (No fix recorded)

7 vendors · 7 products

References

10 links