Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NSummary
CVE-2026-8927 is a critical-severity Authentication Bypass by Capture-replay (CWE-294) vulnerability in Haxx Curl. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Unsecured Credentials (T1552); ranked at the 36th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-4 (Information Flow Enforcement) and SC-8 (Transmission Confidentiality and Integrity) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-41508
Vulnerability Data
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`…
more
erroneously leaks the `Proxy-Authorization:` header intended solely for `proxyA`.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vulnerability causes unintended leakage of Proxy-Authorization credentials/headers across proxy contexts, directly facilitating credential access via T1552 Unsecured Credentials.
Likely ATT&CK TechniquesAI
Techniques this vulnerability likely enables, inferred from its description, weakness type, and attributed-actor tradecraft. Confidence is per-technique.
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
Mitigating Controls (NIST 800-53 r5) AI
SC-8 requires cryptographic protection of transmitted information, directly preventing leakage of sensitive Proxy-Authorization headers across proxy boundaries.
AC-4 enforces information flow policies so that authentication credentials intended for one proxy cannot be sent to another.
SI-7 monitors software integrity and can detect unexpected reuse of stale authentication state in libcurl handles.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Protecting and verifying identity assertions prevents replay of captured authentication material.
Encryption and integrity protections for data-in-transit directly block capture-replay of credentials or tokens.
Network monitoring may detect anomalous replays after the fact but does not prevent the design flaw.
Strong authentication methods can reduce replay risk but do not inherently address captured messages.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Cryptographic protections (e.g., nonces, timestamps, message authentication codes) make captured authentication messages unusable for replay.
Secure authentication mechanisms directly prevent replay attacks by requiring fresh, non-replayable credentials or tokens.
Network security controls such as encryption and integrity protection reduce the feasibility of capturing and replaying authentication traffic.
Application security requirements can mandate replay-resistant authentication designs, but the control itself does not prescribe the technical measures.