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NVD / CVE Program· CNA openssl

CVE-2026-18798: QUIC Server May Trigger Double Free When Processing INITIAL Packet

Noroxi assessment

Priority: Monitor (action score 31/100)

  • 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: 1.6% (FIRST EPSS); higher than 77.1% of all records.
  • 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 3.5.8, 3.6.4, 4.0.2.

Low priority for now. Upgrade to OpenSSL OpenSSL 3.5.8, 3.6.4, 4.0.2 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: QUIC server may double free QRX (QUIC record layer RX) object when channel creation fails for initial packet. Impact summary: Double free leads to heap corruption, which typically results in termination of QUIC server process, leading to Denial of Service. There is so far no evidence that this double free is exploitable for remote code execution, thus it is considered highly improbable. CWE: CWE-415: Double Free Description: In order to validate initial packet, OpenSSL QUIC stack default packet handler (port_default_packet_handler()) creates a so-called QRX object. If the initial packet validates successfully with QRX object, the default packet handler proceeds to channel (connection object) creation. The QRX object used for packet validation is passed to port_bind_channel(), so it becomes part of the newly created connection. If port_bind_channel() fails, then it also frees the QRX object. Once port_bind_channel() returns, the port_default_packet_handler() detects the failure and proceeds to the error branch, where the same QRX object is freed for the second time. The failure in port_bind_channel() function can be induced with a relatively low effort by a malformed (non RFC 9000 compliant) INITIAL packet. If the packet carries DCID (destination connection ID) which is shorter than 8 bytes, then port_bind_channel() jumps to the error path after ossl_quic_lcidm_enrol_odcid() detects that the DCID has invalid length. FIPS impact: no The FIPS module is not affected, as the QUIC implementation is outside of the OpenSSL FIPS module boundary.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Aug 25, 2026
Updated
Sep 23, 2026
EPSS
1.6% · 77th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 1.6%

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.

Follow CVE-2026-18798

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

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Affected systems

Is your version affected?

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VendorProduct
opensslopenssl

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • 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

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10opensslbefore 1:3.5.8-1.el10_2.alma.11:3.5.8-1.el10_2.alma.1
AlmaLinux:10openssl-develbefore 1:3.5.8-1.el10_2.alma.11:3.5.8-1.el10_2.alma.1
AlmaLinux:10openssl-libsbefore 1:3.5.8-1.el10_2.alma.11:3.5.8-1.el10_2.alma.1
AlmaLinux:10openssl-perlbefore 1:3.5.8-1.el10_2.alma.11:3.5.8-1.el10_2.alma.1
AlmaLinux:9opensslbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
AlmaLinux:9openssl-develbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
AlmaLinux:9openssl-libsbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
AlmaLinux:9openssl-perlbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
Alpine:v3.22opensslfrom 3.5.0 · before 3.5.8-r03.5.8-r0
Debian:13opensslbefore 3.5.7-1~deb13u23.5.7-1~deb13u2
Debian:14opensslbefore 3.6.4-13.6.4-1
openSUSE:Leap 16.0openssl-3before 3.5.0-160000.10.13.5.0-160000.10.1
openSUSE:Tumbleweedopenssl-3before 3.5.3-8.13.5.3-8.1
Red Hat:enterprise_linux:10.2opensslbefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-debuginfobefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-debugsourcebefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-develbefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-libsbefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-libs-debuginfobefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:10.2openssl-perlbefore 1:3.5.8-1.el10_21:3.5.8-1.el10_2
Red Hat:enterprise_linux:9::appstreamopenssl-debuginfobefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
Red Hat:enterprise_linux:9::appstreamopenssl-debugsourcebefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
Red Hat:enterprise_linux:9::appstreamopenssl-develbefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8
Red Hat:enterprise_linux:9::appstreamopenssl-libs-debuginfobefore 1:3.5.8-1.el9_81:3.5.8-1.el9_8

+18

Same product

openssl: all records

Other 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 remKEV
    90Now
  • CVE-2021-3711SM2 Decryption Buffer Overflow
    65This 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-2026-14456Aug 13, 2026 · Unbounded Memory Growth in QUIC Server Incoming Channel Queue
    30Monitor
  • ← EarlierCVE-2026-14457Aug 25, 2026 · RPK Server Signature Algorithm Selection Can Dereference a Missing Certificate
    30Monitor
  • Later →CVE-2026-54874Aug 25, 2026 · Excessive Memory Use Buffering DTLS Records for a Future Epoch
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
OpenSSL OpenSSL3.5.8Vendor (CNA)
OpenSSL OpenSSL3.6.4Vendor (CNA)
OpenSSL OpenSSL4.0.2Vendor (CNA)
almalinux:openssl1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10Package registry (OSV)
almalinux:openssl-devel1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10Package registry (OSV)
almalinux:openssl-libs1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10Package registry (OSV)
almalinux:openssl-perl1:3.5.8-1.el10_2.alma.1 · AlmaLinux:10Package registry (OSV)
alpine:openssl3.5.8-r0 · Alpine:v3.22Package registry (OSV)
debian:openssl3.5.7-1~deb13u2 · Debian:13Package registry (OSV)
opensuse:openssl-33.5.3-8.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:openssl0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-config-fips0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-debuginfo1:3.5.8-1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:openssl-devel0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-devel-engine0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-fips-provider-upstream0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-libs0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-perl0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl30:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl3-devel0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl3-devel-engine0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl3-libs0:3.5.8-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
rocky linux:openssl1:3.5.8-1.el10_2 · Rocky Linux:10Package registry (OSV)
suse:openssl-33.5.0-160000.10.1 · SUSE:Linux Micro 6.2Package 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.

EPSS, last 120 days

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 researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-3518877 days apartDouble-free When Checking OCSP Stapled Response
    20Monitor

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-415 · Double Free

CVSS 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.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records