USN-8847-1: OpenSSL vulnerabilities
Ubuntu warned of OpenSSL flaws that could cause denial of service or a timing side-channel leak.
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Vulnerability1 · 1 read
CVE-2026-35191
OpenSSL QUIC amplification when address validation is off
- CVSS 3.1
- 3.7 low
- EPSS
- —
- Published
- ·
- Modified
AI analysisSummaries by Vani AI
CVE-2026-35191 is an expected-behavior flaw (CWE-440) in the OpenSSL QUIC server. When the server is configured not to validate client addresses, it can count one incoming datagram more than once toward unvalidated credit, so it may send more than the RFC 9000 limit of three times the data actually received. A remote attacker who can spoof packets to that server could use the extra responses to amplify a denial-of-service attack; this is not code execution or data theft, and FIPS modules are unaffected because QUIC sits outside the FIPS boundary. Only OpenSSL QUIC servers with address validation disabled are in scope, and the advisory data does not name version ranges. No public proof of concept is known and the CVE is not in CISA KEV.
What to do: Keep client address validation enabled on OpenSSL QUIC servers so the unvalidated amplification limit is not relied on. Apply the OpenSSL and OS updates covered by USN-8847-1 for your packages, and check QUIC server config for address validation being turned off. FIPS modules are not affected.
| Product | Affected |
|---|---|
| OpenSSL (QUIC server) | — |
Estimated exposure
No basis for an estimate.
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description · NVD
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.