CVE-2026-8927

Description

When reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration, libcurl fails to clear the proxy authentication state between requests. Specifically, if the initial transfer authenticates against `proxyA` using Digest auth, a subsequent transfer routed through `proxyB` erroneously leaks the `Proxy-Authorization:` header intended solely for `proxyA`.

CVSS Metrics

• v3.1•CRITICAL•Score: 9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
• v3.1•HIGH•Score: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Trends

Current EPSS score: 0.50%• Percentile: 42%

Techniques & Countermeasures

• CWE-294•Authentication Bypass by Capture-replay

  A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes).

Affected Systems

• alpine•curl

  ≥ 7.12.0, < 8.22.0-r0 | ≥ 7.12.0, < 8.21.0-r0

• chainguard•eco-python-curl

  < 8.21.0-r0

• chainguard•eco-python-curl-minimal

  < 8.21.0-r0

• chainguard•eco-python-curl-minimal-bin

  < 8.21.0-r0

• chainguard•eco-python-curl-minimal-dev

  < 8.21.0-r0

• chainguard•eco-python-curl-minimal-doc

  < 8.21.0-r0

• chainguard•eco-python-curl-minimal-static

  < 8.21.0-r0

• chainguard•eco-python-curl-nghttp2

  < 8.21.0-r0

• chainguard•eco-python-curl-nghttp2-bin

  < 8.21.0-r0

• chainguard•eco-python-curl-nghttp2-dev

  < 8.21.0-r0

• chainguard•eco-python-curl-nghttp2-static

  < 8.21.0-r0

• chainguard•libcurl4

  all

• wolfi•libcurl4

  all

• curl•curl

  8.20.0 | 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 | 7.14.0 | 7.13.2 | 7.13.1 | 7.13.0 | 7.12.3 | 7.12.2 | 7.12.1 | 7.12.0 | ≥ 7.12.0, < 8.14.2 | ≥ 8.15.0, < 8.16.1 | ≥ 8.17.0, < 8.20.1 | ≥ fc6eff13b5414caf6edf22d73a3239e074a04216, < 5c225384b8d52c67ce8259c6e4203bc57aacb567 | 8.20.0 | 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 | 7.14.0 | 7.13.2 | 7.13.1 | 7.13.0 | 7.12.3 | 7.12.2 | 7.12.1 | 7.12.0

• debian•curl

  all | all | all | < 8.21.0~rc2-1

• haxx•curl

  ≥ 7.12.0, < 8.21.0

• redhat•curl

  < 0:8.12.1-4.el10_2.4

• redhat•curl-debuginfo

  < 0:8.12.1-4.el10_2.4

• redhat•curl-debugsource

  < 0:8.12.1-4.el10_2.4

• redhat•libcurl

  < 0:8.12.1-4.el10_2.4

• redhat•libcurl-debuginfo

  < 0:8.12.1-4.el10_2.4

• redhat•libcurl-devel

  < 0:8.12.1-4.el10_2.4

• redhat•libcurl-minimal

  < 0:8.12.1-4.el10_2.4

• redhat•libcurl-minimal-debuginfo

  < 0:8.12.1-4.el10_2.4

References (13)

• https://curl.se/docs/CVE-2026-8927.json
• https://curl.se/docs/CVE-2026-8927.html
• https://hackerone.com/reports/3744543
• https://security-tracker.debian.org/tracker/CVE-2026-8927
• https://access.redhat.com/errata/RHSA-2026:55432
• https://access.redhat.com/security/updates/classification/#important
• https://bugzilla.redhat.com/show_bug.cgi?id=2496769
• https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_55432.json
• https://access.redhat.com/security/cve/CVE-2026-8927
• https://www.cve.org/CVERecord?id=CVE-2026-8927
• https://nvd.nist.gov/vuln/detail/CVE-2026-8927
• https://security.alpinelinux.org/vuln/CVE-2026-8927
• https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/8xxx/CVE-2026-8927.json