# CVE-2026-35191: QUIC Unvalidated Amplification Credit may be Over Accounted CVE-2026-35191 is fixed in 14 products on 1 platform, first by libssl3t64 3.5.5-1ubuntu3.6, released September 28, 2026. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2026-35191 - Priority: Routine - CVSS: 3.7 (Low) - EPSS: 0.0072 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Sep 28, 2026 - Weakness: Expected Behavior Violation - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-35191 ## 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | libssl3t64 Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.6 | [libssl3t64 3.5.5-1ubuntu3.6](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libssl3t64-3.5.5-1ubuntu3.6.md) | Sep 28, 2026 | | Linux | openssl Debian 13.5 (trixie) | 3.5.7-1~deb13u3 | [DEBIAN-CVE-2026-35191](https://patchblox.com/security/data/fix/linux/debian-cve-2026-35191.md) | Sep 30, 2026 | | Linux | openssl Debian 14 | 3.6.5-1 | [DEBIAN-CVE-2026-35191](https://patchblox.com/security/data/fix/linux/debian-cve-2026-35191.md) | Sep 30, 2026 | | Linux | openssl Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.6 | [openssl 3.5.5-1ubuntu3.6](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-openssl-3.5.5-1ubuntu3.6.md) | Sep 28, 2026 | | Linux | openssl amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-3 opensuse-leap 16.0 | 3.5.0-160000.11.1 | [OPENSUSE-SU-2026:22102-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22102-1.md) | Nov 7, 2026 | | Linux | openssl-3 sles 15.7 | 3.5.0-150700.5.53.2 | [SUSE-SU-2026:4414-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4414-1.md) | Oct 2, 2026 | | Linux | openssl-3 sles 16.0 | 3.5.0-160000.11.1 | [SUSE-SU-2026:24245-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24245-1.md) | Nov 7, 2026 | | Linux | openssl-debuginfo amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-debugsource amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-devel amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-fips-provider-latest amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-fips-provider-latest-debuginfo amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-libs amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-libs-debuginfo amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-perl amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-provider-legacy Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.6 | [openssl-provider-legacy 3.5.5-1ubuntu3.6](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-openssl-provider-legacy-3.5.5-1ubuntu3.6.md) | Sep 28, 2026 | | Linux | openssl-snapsafe-libs amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | | Linux | openssl-snapsafe-libs-debuginfo amzn 2023 | 1:3.5.8-1.amzn2023.0.3 | [ALAS2023-2026-3204](https://patchblox.com/security/data/fix/linux/alas2023-2026-3204.md) | Nov 7, 2026 | --- Data as of 2026-11-08T00:53:09Z UTC. 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