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Vulnerabilities

Vulnerability · CVE-2026-35191

QUIC Unvalidated Amplification Credit may be Over Accounted

Published Sep 29, 2026 · catalog updated Sep 30, 2026 · OpenSSL OpenSSL

Last checked Oct 27, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-35191. EPSS is 0.72%. Act only if a listed version of OpenSSL OpenSSL is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Low3.7
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.72%
Remediation
Advisory link
Affected products
vendor OpenSSL OpenSSL

Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be forced to count incoming packets multiple times in its unvalidated credit computation, leading to a violation of the RFC 9000 unvalidated connection amplification limit of 3 times the amount of data received. Impact summary: A remote attacker able to spoof packets to a server using the OpenSSL QUIC implementation might use the server for an amplification of a DDoS attack. CWE: CWE-440: Expected Behavior Violation Description: OpenSSL's QUIC stack, when operating as a server, enforces client address validation (RFC 9000, Section 8), to confirm the peer address is not used for a traffic amplification attack. If this feature is disabled on the server, the QUIC stack limits the amount of server data that can be sent to 3 times the amount of data received from the peer address, until such time as the TLS handshake is completed. The OpenSSL QUIC server, when operating in non-validation mode, adds the length of the whole datagram received to the unvalidated credit limit when processing each QUIC packet in the datagram. A remote peer may, after establishing a connection with an initial client hello frame, send a subsequent datagram containing multiple QUIC packets, leading the server to account the entire datagram length for each packet in the datagram, resulting in the server believing that the peer has sent more data than it actually has, thereby violating the 3x amplification limit mandated by the RFC. FIPS impact: no As the QUIC stack lives outside the FIPS module boundary, no FIPS modules are affected by this CVE.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

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  • vendor OpenSSL OpenSSLversion unspecified

How to fix CVE-2026-35191

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-35191. EPSS is 0.72%. Act only if a listed version of OpenSSL OpenSSL is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-440. EPSS 0.72%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 30, 2026 · CVE.org

    Updated

    Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be forced to count incoming packets multiple times in its unvalidated credit computation, leading to a violation of the RFC 9000 unvalidated connection amplification limit of 3 times the amount of data received. Impact summary: A remote attacker able to spoof packets to a server using the OpenSSL QUIC im

  2. Oct 27, 2026 · BSI CERT-Bund

    Detected

    CVE-2026-35191 is listed by OpenSSL: Mehrere Schwachstellen.

Sources

  • BSI CERT-BundGovernment advisoryCVE-2026-35191

    OpenSSL: Mehrere Schwachstellen

    wid.cert-bund.de
  • CVE.orgVulnerability recordCVE-2026-35191

    Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be forced to count incoming packets multiple times in its unvalidated credit computation, leading to a violation of the RFC 9000 unvalidated connection amplification limit of 3 times th

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-35191

    30-day exploitation probability 0.72%

    first.org

References

Freshness

Last verified in this catalog Oct 27, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgOct 27, 2026
  • BSI CERT-BundOct 27, 2026
  • FIRST EPSSOct 27, 2026