CVE-2026-35191QUIC Unvalidated Amplification Credit may be Over Accounted
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 3.7 LOW (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
- Weakness (CWE)
- CWE-440
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- openssl
- NVD analysis
- Analyzed
- Record last updated
- Sep 30, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
OpenSSL OpenSSL openssl:openssl (from the name) | from 4.0.0 before 4.0.3; from 3.6.0 before 3.6.5; from 3.5.0 before 3.5.9 | CNA record |
openssl openssl openssl:openssl | from 3.5.0 before 3.5.9; from 3.6.0 before 3.6.5; from 4.0.0 before 4.0.3 | NVD |
References
- https://openssl-library.org/news/secadv/20260929.txtvendor-advisory
- https://github.com/openssl/openssl/commit/e44292e58b090014232ef75bd400393851b24d1apatch
- https://github.com/openssl/openssl/commit/2de4c35fb13fc58f43fd8dc1d261700472ce72e5patch
- https://github.com/openssl/openssl/commit/0fe4442d4f8ea3af8a174046dae176e0d4717239patch
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.