CVE-2025-13034Network attack vector

Server impersonation via conditional public-key pin check

Published Jan 8, 2026 · Updated Jan 8, 2026

Certificate validation bypass in curl 8.8.0 through 8.17.0 allows man-in-the-middle attackers to impersonate HTTP/3 servers. In lib/vquic/vquic-tls.c, the GnuTLS branch calls Curl_gtls_verifyserver only when verifyhost is enabled, so disabling hostname checks also suppresses the configured public-key pin check. The bypass requires QUIC through ngtcp2 built with GnuTLS, an explicit pinned public key, and disabled standard certificate verification; HTTP/1, HTTP/2, and other QUIC or TLS backends remain unaffected.

CVSS severity5.9
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Certificate validation bypass in curl 8.8.0 through 8.17.0 allows man-in-the-middle attackers to impersonate HTTP/3 servers. In lib/vquic/vquic-tls.c, the GnuTLS branch calls Curl_gtls_verifyserver only when verifyhost is enabled, so disabling hostname checks also suppresses the configured public-key pin check. The bypass requires QUIC through ngtcp2 built with GnuTLS, an explicit pinned public key, and disabled standard certificate verification; HTTP/1, HTTP/2, and other QUIC or TLS backends remain unaffected.

The record

CVE
CVE-2025-13034
Published
Jan 8, 2026
Updated
Jan 8, 2026
Vendor
curl
Product
curl
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=8.10.0 <=8.10.0
  2. Affected versionversion=8.10.1 <=8.10.1
  3. Affected versionversion=8.11.0 <=8.11.0
  4. Affected versionversion=8.11.1 <=8.11.1
  5. Affected versionversion=8.12.0 <=8.12.0
  6. Affected versionversion=8.12.1 <=8.12.1
  7. Affected versionversion=8.13.0 <=8.13.0
  8. Affected versionversion=8.14.0 <=8.14.0
  9. Affected versionversion=8.14.1 <=8.14.1
  10. Affected versionversion=8.15.0 <=8.15.0
  11. Affected versionversion=8.16.0 <=8.16.0
  12. Affected versionversion=8.17.0 <=8.17.0
  13. Affected versionversion=8.8.0 <=8.8.0
  14. Affected versionversion=8.9.0 <=8.9.0
  15. Affected versionversion=8.9.1 <=8.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

curl · curlversion=8.10.0 <=8.10.0; version=8.10.1 <=8.10.1; version=8.11.0 <=8.11.0; version=8.11.1 <=8.11.1; version=8.12.0 <=8.12.0; version=8.12.1 <=8.12.1; version=8.13.0 <=8.13.0; version=8.14.0 <=8.14.0; version=8.14.1 <=8.14.1; version=8.15.0 <=8.15.0; version=8.16.0 <=8.16.0; version=8.17.0 <=8.17.0; version=8.8.0 <=8.8.0; version=8.9.0 <=8.9.0; version=8.9.1 <=8.9.1

Published CVSS scores

5.9CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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