CVE-2026-35191
Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be…
- Risk score
- 43/100
- CVSS
- 3.7 v3.1
- Exploit chance (30 days)
- 0.7%
- Published
- 29 Sep 2026
Open in the live forecast Today's forecast
What to know
- What it is
- 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 summa…
- Affected
- OpenSSL
- Fix
- Apply the vendor's security update; see the linked advisory.
- Exploitation
- No known exploitation
Story map
At a glance
OpenSSL: Amber, patch this week. Issue summary: The DTLS retransmission logic does not correctly handle a handshake message write that is suspended part-way through. The retransmitted message can be read past the message buffer and the retransmission overwrites the internal state the suspended write needs to resume correctly. Impact summary: The retr…
The flaws
- CVE-2026-35191: Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be… (CVSS 3.7 · EPSS 1%)
- CVE-2026-84782: Out-of-bounds read can lead to denial of service (CVSS 8.2 · EPSS 1%)
- CVE-2026-54873: Denial of service (CVSS 7.5 · EPSS 1%)
- CVE-2026-84784: Denial of service (CVSS 7.5 · EPSS 1%)
The fix
Fix: Apply the vendor's security update; see the linked advisory.
Who is exposed: OpenSSL
Where it stands
- No known exploitation
Connects to
- Same weakness: CWE-440 (CWE-440). 2 other warnings in 30 days
- Same product: Earlier OpenSSL warnings. 10 in the last 90 days
Why it is Yellow
- CVSS 3.7 low
- On your watchlist: openssl
References
Original description
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.
Last activity 29 Sep 2026. Patch Forecast updates every hour.