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.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (3.7): severity, escalated by confirmed exploitation. This CVE's 3.7 is its impact severity (EG Severity), not escalated.
- EG Severity
- 3.7 LOWCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.7% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-29). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it