Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be forced to count incoming packets multiple times in… (CVE-2026-35191)
The OpenSSL QUIC server, when configured to disable client address validation, can incorrectly count incoming packets multiple times in its unvalidated credit computation. This leads to a violation of the RFC 9000 amplification limit, allowing the server to send up to three times more data than it actually receives from a peer address. This flaw can be exploited by a remote attacker capable of spoofing packets to amplify a DDoS attack.
AI Analysis
Technical Summary
OpenSSL's QUIC server implementation enforces client address validation per RFC 9000 to prevent amplification attacks. When this validation is disabled, the server limits data sent to three times the data received from the peer until the TLS handshake completes. However, the server incorrectly adds the entire datagram length to the unvalidated credit for each QUIC packet within that datagram. An attacker can send a datagram with multiple QUIC packets, causing the server to overcount received data and violate the amplification limit. This flaw can be exploited to amplify DDoS attacks by spoofing packets.
Potential Impact
A remote attacker able to spoof packets to an OpenSSL QUIC server configured without address validation can cause the server to exceed the RFC 9000 amplification limit. This may enable the attacker to use the server as an amplifier in distributed denial-of-service (DDoS) attacks, increasing the volume of traffic directed at a target.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, it is recommended to ensure that client address validation is enabled on OpenSSL QUIC servers to enforce the amplification limit as specified by RFC 9000.
Issue summary: The OpenSSL QUIC server, when configured to not preform address validation, can be forced to count incoming packets multiple times in… (CVE-2026-35191)
Description
The OpenSSL QUIC server, when configured to disable client address validation, can incorrectly count incoming packets multiple times in its unvalidated credit computation. This leads to a violation of the RFC 9000 amplification limit, allowing the server to send up to three times more data than it actually receives from a peer address. This flaw can be exploited by a remote attacker capable of spoofing packets to amplify a DDoS attack.
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
OpenSSL's QUIC server implementation enforces client address validation per RFC 9000 to prevent amplification attacks. When this validation is disabled, the server limits data sent to three times the data received from the peer until the TLS handshake completes. However, the server incorrectly adds the entire datagram length to the unvalidated credit for each QUIC packet within that datagram. An attacker can send a datagram with multiple QUIC packets, causing the server to overcount received data and violate the amplification limit. This flaw can be exploited to amplify DDoS attacks by spoofing packets.
Potential Impact
A remote attacker able to spoof packets to an OpenSSL QUIC server configured without address validation can cause the server to exceed the RFC 9000 amplification limit. This may enable the attacker to use the server as an amplifier in distributed denial-of-service (DDoS) attacks, increasing the volume of traffic directed at a target.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, it is recommended to ensure that client address validation is enabled on OpenSSL QUIC servers to enforce the amplification limit as specified by RFC 9000.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-5p85-47cf-3663
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-35191"]
Threat ID: 6abc27c5680226ef6846f82d
Added to database: 09/29/2026, 21:04:05 UTC
Last enriched: 09/29/2026, 21:19:38 UTC
Last updated: 09/30/2026, 03:15:31 UTC
Views: 3
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