CVE-2026-63075: QUIC ACK-only Packet Retention Can Cause Memory Exhaustion
Noroxi assessment
Priority: Monitor (action score 30/100)
- 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: 0.57% (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 3.4.7, 3.5.8, 3.6.4; azl3 openssl 3.3.7-6 on Azure Linux 3.0 3.3.7-6.
Low priority for now. Upgrade to OpenSSL OpenSSL 3.4.7, 3.5.8, 3.6.4; azl3 openssl 3.3.7-6 on Azure Linux 3.0 3.3.7-6 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: When OpenSSL processes QUIC traffic from a peer that repeatedly sends ack-eliciting packets while not acknowledging ACK-only responses, the QUIC stack can retain ACK-only packet metadata for the lifetime of the connection. Impact summary: A remote peer that can complete a QUIC handshake can cause connection-scoped memory growth which may lead to Denial of Service through memory exhaustion, especially with sustained traffic or many concurrent QUIC connections. CWE: CWE-770: Allocation of Resources Without Limits or Throttling Description: When the OpenSSL QUIC stack sends an ACK-only packet, there is no requirement by the QUIC protocol that the peer will acknowledge that ACK-only packet (i.e. it is itself not ack-eliciting). However, the OpenSSL implementation stores the metadata about the ACK frames regardless. In and of itself that's ok, but if a malicious peer establishes a connection, and then drives the connection such that ACK-only packets are forced from the OpenSSL implementation peer (i.e., by sending numerous PING frames), and then withholding any subsequent acks for ack-eliciting data, like legitimate data, said malicious peer can force inappropriate memory growth on the OpenSSL peer, potentially leading to a Denial of Service. The fix is to ensure that we account for the transmission of the ACK-only packet in the packet histories high and low watermark without actually storing the ACK-only packet metadata itself. FIPS impact: no The OpenSSL FIPS module is not affected as the QUIC code is outside the FIPS module boundary.
- Published
- Aug 25, 2026
- Updated
- Sep 11, 2026
- EPSS
- 0.5% · 47th percentile
- CWE
- CWE-770
Report tools
Action score
30
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.5%
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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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 3.4.7
- openssl openssl3.5.0 and later · before 3.5.8
- openssl openssl3.6.0 and later · before 3.6.4
- openssl openssl4.0.0 and later · before 4.0.2
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 4.0.2affected · semver
- 3.6.0 and later · before 3.6.4affected · semver
- 3.5.0 and later · before 3.5.8affected · semver
- 3.4.0 and later · before 3.4.7affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:10 | openssl | before 1:3.5.8-1.el10_2.alma.1 | 1:3.5.8-1.el10_2.alma.1 |
| AlmaLinux:10 | openssl-devel | before 1:3.5.8-1.el10_2.alma.1 | 1:3.5.8-1.el10_2.alma.1 |
| AlmaLinux:10 | openssl-libs | before 1:3.5.8-1.el10_2.alma.1 | 1:3.5.8-1.el10_2.alma.1 |
| AlmaLinux:10 | openssl-perl | before 1:3.5.8-1.el10_2.alma.1 | 1:3.5.8-1.el10_2.alma.1 |
| AlmaLinux:9 | openssl | before 1:3.5.8-1.el9_8 | 1:3.5.8-1.el9_8 |
| AlmaLinux:9 | openssl-devel | before 1:3.5.8-1.el9_8 | 1:3.5.8-1.el9_8 |
| AlmaLinux:9 | openssl-libs | before 1:3.5.8-1.el9_8 | 1:3.5.8-1.el9_8 |
| AlmaLinux:9 | openssl-perl | before 1:3.5.8-1.el9_8 | 1:3.5.8-1.el9_8 |
| Alpine:v3.22 | openssl | from 3.4.0 · before 3.5.8-r0 | 3.5.8-r0 |
| Debian:13 | openssl | before 3.5.7-1~deb13u2 | 3.5.7-1~deb13u2 |
| Debian:14 | openssl | before 3.6.4-1 | 3.6.4-1 |
| openSUSE:Leap 16.0 | openssl-3 | before 3.5.0-160000.10.1 | 3.5.0-160000.10.1 |
| openSUSE:Tumbleweed | openssl-3 | before 3.5.3-8.1 | 3.5.3-8.1 |
| Red Hat:enterprise_linux:10.2 | openssl | before 1:3.5.8-1.el10_2 | 1:3.5.8-1.el10_2 |
| Red Hat:enterprise_linux:10.2 | openssl-debuginfo | before 1:3.5.8-1.el10_2 | 1:3.5.8-1.el10_2 |
| Red Hat:enterprise_linux:10.2 | openssl-debugsource | before 1:3.5.8-1.el10_2 | 1:3.5.8-1.el10_2 |
| Red Hat:enterprise_linux:10.2 | openssl-devel | before 1:3.5.8-1.el10_2 | 1:3.5.8-1.el10_2 |
| Red Hat:enterprise_linux:10.2 | openssl-libs | before 1:3.5.8-1.el10_2 | 1:3.5.8-1.el10_2 |
| Red Hat:enterprise_linux:10.2 | openssl-libs-debuginfo | before 1:3.5.8-1.el10_2 | 1:3.5.8-1.el10_2 |
| Red Hat:enterprise_linux:10.2 | openssl-perl | before 1:3.5.8-1.el10_2 | 1:3.5.8-1.el10_2 |
| Red Hat:enterprise_linux:9::appstream | openssl-debuginfo | before 1:3.5.8-1.el9_8 | 1:3.5.8-1.el9_8 |
| Red Hat:enterprise_linux:9::appstream | openssl-debugsource | before 1:3.5.8-1.el9_8 | 1:3.5.8-1.el9_8 |
| Red Hat:enterprise_linux:9::appstream | openssl-devel | before 1:3.5.8-1.el9_8 | 1:3.5.8-1.el9_8 |
| Red Hat:enterprise_linux:9::appstream | openssl-libs-debuginfo | before 1:3.5.8-1.el9_8 | 1:3.5.8-1.el9_8 |
+7
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…KEV90Now
- 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-2026-63073Aug 25, 2026 · Untrusted Sender DN Used as Format String in CMP Response Validation39Monitor
- ← EarlierCVE-2026-63074Aug 25, 2026 · CMP Indefinite Cache Growth of ExtraCerts23Monitor
- Later →CVE-2026-63076Aug 25, 2026 · Invalid Pointer Dereference in CMP Server via Crafted protectionAlg30Monitor
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 | 3.4.7 | Vendor (CNA) |
| OpenSSL OpenSSL | 3.5.8 | Vendor (CNA) |
| OpenSSL OpenSSL | 3.6.4 | Vendor (CNA) |
| OpenSSL OpenSSL | 4.0.2 | Vendor (CNA) |
| azl3 openssl 3.3.7-6 on Azure Linux 3.0 | 3.3.7-6 | Microsoft (MSRC) |
| almalinux:openssl | 1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10 | Package registry (OSV) |
| almalinux:openssl-devel | 1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10 | Package registry (OSV) |
| almalinux:openssl-libs | 1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10 | Package registry (OSV) |
| almalinux:openssl-perl | 1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10 | Package registry (OSV) |
| alpine:openssl | 3.5.8-r0 · Alpine:v3.22 | Package registry (OSV) |
| debian:openssl | 3.5.7-1~deb13u2 · Debian:13 | Package registry (OSV) |
| opensuse:openssl-3 | 3.5.3-8.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| red hat:openssl | 1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:openssl-debuginfo | 1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:openssl-debugsource | 1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:openssl-devel | 1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:openssl-libs | 1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:openssl-libs-debuginfo | 1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:openssl-perl | 1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| rocky linux:openssl | 1:3.5.8-1.el10_2 · Rocky Linux:10 | Package registry (OSV) |
| suse:openssl-3 | 3.5.0-160000.10.1 · 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.
No dated events beyond publication.
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.
- Neil Hormanremediation developer
- Opal Wright (TrailBits)reporter
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-1445612 days apartUnbounded Memory Growth in QUIC Server Incoming Channel Queue30Monitor
- CVE-2026-5487335 days apartQUIC STREAM Fragment Metadata DoS30Monitor
- CVE-2026-8478435 days apartQUIC: Unbounded RETIRE_CONNECTION_ID Backlog30Monitor
- CVE-2026-630740 days apartCMP Indefinite Cache Growth of ExtraCerts23Monitor
- CVE-2026-3518935 days apartExcessive Memory Allocation in Relative CRLDP Processing21Monitor
- CVE-2026-7580435 days apartQUIC Connection-Level Flow Control is Not Enforced for Streams21Monitor
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).
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
- high · 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
- High
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:H
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
- Fix✗ → ✓
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.