CVE-2026-75804: QUIC Connection-Level Flow Control is Not Enforced for Streams
Noroxi assessment
Priority: Monitor (action score 21/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.35% (FIRST EPSS).
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- According to CISA the attack is automatable: targets can be found by mass scanning.
- Fixed version: OpenSSL OpenSSL 3.4.8, 3.5.9, 3.6.5; azl3 openssl 3.3.7-6 on Azure Linux 3.0 3.3.7-7.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to OpenSSL OpenSSL 3.4.8, 3.5.9, 3.6.5; azl3 openssl 3.3.7-6 on Azure Linux 3.0 3.3.7-7 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
Issue summary: OpenSSL QUIC stack does not enforce connection level flow control for streams. Remote peers may send more bytes as long as they fit within the stream flow control limits. Impact summary: A malicious remote peer may exploit the lack of connection flow control for streams to make the QUIC stack receive ~100MB of memory instead of 768 KiB (default flow control window size). CWE: CWE-770: Allocation of Resources Without Limits or Throttling Description: The local QUIC stack advertises two flow control limits to its remote peer: stream flow control limit and connection flow control limit. The remote peer must follow both limits when transmitting stream data. Whenever the local QUIC stack receives a stream frame, it validates that the size of the received stream frame stays within flow control limits. If either limit is exceeded (stream level or connection level), then the QUIC stack must close the connection with a flow control error. The vulnerable OpenSSL QUIC stack enforces the stream-level but not the connection-level limit. To exploit the issue, three conditions must be met: - the remote peer opens several streams - each stream must stay within the stream-level flow control limit - there must be no zero-offset byte sent on any of the streams (to prevent the vulnerable QUIC stack from consuming data). By meeting the conditions above, the remote peer may make the local stack allocate 2 x MAX_STREAMS x (stream flow control limit) bytes of memory. MAX_STREAMS defaults to 100, and the limit applies to both bidirectional and unidirectional streams, making it 200 in total. The default flow control window for a stream is 512kB. The remote peer may force the vulnerable QUIC stack to allocate 100MB of heap per connection. FIPS impact: no The FIPS module is not affected as the QUIC implementation is outside of the OpenSSL FIPS module boundary.
- Published
- Sep 29, 2026
- Updated
- Oct 8, 2026
- EPSS
- 0.3% · 27th percentile
- CWE
- CWE-770
Report tools
Action score
21
Monitor
Low priority for now.
- CVSS
- 21 / 40 · 5.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| openssl | openssl | cpe:2.3:a:openssl:openssl |
Check your server's TLS configuration
The OpenSSL version can't be seen from outside; the free SSL checker tests your certificate, enabled TLS versions and weak ciphers. Confirm the version on your server with the package manager.
Run the SSL checkAffected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- openssl openssl3.4.0 and later · before 3.4.8
- openssl openssl3.5.0 and later · before 3.5.9
- openssl openssl3.6.0 and later · before 3.6.5
- openssl openssl4.0.0 and later · before 4.0.3
Versions reported by the vendor
Affected version ranges reported by the assigning authority (openssl). Independent of NVD's CPE analysis and usually ahead of it.
OpenSSL OpenSSL
- 4.0.0 and later · before 4.0.3affected · semver
- 3.6.0 and later · before 3.6.5affected · semver
- 3.5.0 and later · before 3.5.9affected · semver
- 3.4.0 and later · before 3.4.8affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.21 | openssl | from 3.4.0 · before 3.3.7-r2 | 3.3.7-r2 |
| Debian:13 | openssl | before 3.5.7-1~deb13u3 | 3.5.7-1~deb13u3 |
| Debian:14 | openssl | before 3.6.5-1 | 3.6.5-1 |
| openSUSE:Leap 16.0 | openssl-3 | before 3.5.0-160000.11.1 | 3.5.0-160000.11.1 |
| Red Hat:hummingbird:1 | openssl | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl-config-fips | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl-devel | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl-devel-engine | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl-fips-provider-upstream | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl-libs | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl-perl | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl3 | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl3-devel | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl3-devel-engine | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| Red Hat:hummingbird:1 | openssl3-libs | before 0:3.5.9-0.1.hum1 | 0:3.5.9-0.1.hum1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP7 | openssl-3 | before 3.5.0-150700.5.53.2 | 3.5.0-150700.5.53.2 |
| SUSE:Linux Micro 6.2 | openssl-3 | before 3.5.0-160000.11.1 | 3.5.0-160000.11.1 |
Same product
openssl: all recordsOther highest-scoring records for the same primary product.
- CVE-2014-0160The (1) TLS and (2) DTLS implementations in OpenSSL 1.0.1 before 1.0.1g do not properly handle Heartbeat Extension packets, which allows remKEV90Now
- CVE-2021-3711SM2 Decryption Buffer Overflow65This week
- CVE-2003-0545Double free vulnerability in OpenSSL 0.9.7 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code 65This week
Published before and after this one in the same product
- ← EarlierCVE-2026-54875Sep 29, 2026 · Non-Constant-Time SM2 Scalar Multiplication on ARM64 and RISC-V14Monitor
- ← EarlierCVE-2026-72897Sep 29, 2026 · Out-of-Bounds Access After SSL_set_SSL_CTX() During a Handshake30Monitor
- Later →CVE-2026-75805Sep 29, 2026 · NULL Pointer Dereference in CMP Client Revocation Response Handling21Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| OpenSSL OpenSSL | 3.4.8 | Vendor (CNA) |
| OpenSSL OpenSSL | 3.5.9 | Vendor (CNA) |
| OpenSSL OpenSSL | 3.6.5 | Vendor (CNA) |
| OpenSSL OpenSSL | 4.0.3 | Vendor (CNA) |
| azl3 openssl 3.3.7-6 on Azure Linux 3.0 | 3.3.7-7 · Release Notes | Microsoft (MSRC) |
| alpine:openssl | 3.3.7-r2 · Alpine:v3.21 | Package registry (OSV) |
| debian:openssl | 3.5.7-1~deb13u3 · Debian:13 | Package registry (OSV) |
| opensuse:openssl-3 | 3.5.0-160000.11.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| red hat:openssl | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl-config-fips | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl-devel | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl-devel-engine | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl-fips-provider-upstream | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl-libs | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl-perl | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl3 | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl3-devel | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl3-devel-engine | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssl3-libs | 0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| suse:openssl-3 | 3.5.0-150700.5.53.2 · SUSE:Linux Enterprise Module for Basesystem 15 SP7 | Package registry (OSV) |
| suse:openssl-3 | 3.5.0-160000.11.1 · SUSE:Linux Micro 6.2 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Published
- Fix recordedsame day
- TodayOct 26, 2026+26 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- Moltenbitreporter
- Bhabani Sankar Dasreporter
- Saiyowa Security Teamreporter
- Alexandr Nedvedickyremediation developer
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-548730 days apartQUIC STREAM Fragment Metadata DoS30Monitor
- CVE-2026-847840 days apartQUIC: Unbounded RETIRE_CONNECTION_ID Backlog30Monitor
- CVE-2026-6307535 days apartQUIC ACK-only Packet Retention Can Cause Memory Exhaustion30Monitor
- CVE-2026-1445647 days apartUnbounded Memory Growth in QUIC Server Incoming Channel Queue30Monitor
- CVE-2026-6307435 days apartCMP Indefinite Cache Growth of ExtraCerts23Monitor
- CVE-2026-351890 days apartExcessive Memory Allocation in Relative CRLDP Processing21Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-26-1218 · Sep 30, 2026(OpenSSL Güvenlik Zafiyeti)
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- low · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- Low
Weakness class (CWE)
CWE-770 · Allocation of Resources Without Limits or ThrottlingCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- FloodingCAPEC-125likelihood: High · Medium
- Excessive AllocationCAPEC-130likelihood: Medium · Medium
- XML Ping of the DeathCAPEC-147likelihood: Low · Medium
- Exponential Data ExpansionCAPEC-197likelihood: High · Medium
- Serialized Data Parameter BlowupCAPEC-229likelihood: High · High
- Serialized Data with Nested PayloadsCAPEC-230likelihood: Medium · High
- Oversized Serialized Data PayloadsCAPEC-231likelihood: Medium · High
- HTTP DoSCAPEC-469Low
ATT&CK techniques
- Network Denial of Service:Direct Network FloodT1498.001
- Network Denial of Service:Reflection AmplificationT1498.002
- Endpoint Denial of ServiceT1499
- Endpoint Denial of Service: OS Exhaustion FloodT1499.001
- Endpoint Denial of Service:Service Exhaustion FloodT1499.002
- Endpoint Denial of Service:Application Exhaustion FloodT1499.003
Change log
- Exploit maturity— → none
- Fix✗ → ✓
- CVSS— → 5.3
- Severity— → medium
- SSVC exploitation— → none
For records you follow, these changes also arrive as notifications. →
References
Show all references (4 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.