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CVE.org (no NVD analysis yet)· CNA openssl

CVE-2026-42772: Potential CPU DoS via O(n^2) Fragment Reassembly in QUIC

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: 0.49% (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: The QUIC stream reassembly algorithm performance deteriorates progressively as packets are arriving out of order. The worst case has a quadratic complexity proportional to the number of stream frames kept in the buffer for the received stream data. Impact summary: A remote QUIC peer that completes the handshake can create a connection-scoped CPU pressure and potentially a Denial of Service using compliant STREAM frames inside the advertised receive window, with low attacker bandwidth. CWE: CWE-407: Inefficient Algorithmic Complexity Description: OpenSSL manages received QUIC stream fragments using a doubly-linked list. While it optimizes for append operations (at the end of the list), it falls back to a head-to-tail linear search for any fragment that does not immediately follow the current `tail`. By manipulating the sequence of offsets, an attacker can force the server to perform O(n^2) operations, consuming excessive CPU time for the QUIC process. FIPS impact: no The FIPS module is not affected as the QUIC implementation is outside of the OpenSSL FIPS module boundary.

MediumCVSS 5.3 · v3.1—No exploit Fix available
Published
Sep 29, 2026
Updated
Oct 8, 2026
EPSS
0.4% · 42th percentile

Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

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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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?

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.

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 openssl3.4.0 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.

EcosystemPackageAffected rangeFix
Debian:13opensslbefore 3.5.7-1~deb13u33.5.7-1~deb13u3
Debian:14opensslbefore 3.6.5-13.6.5-1
Red Hat:hummingbird:1opensslbefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl-config-fipsbefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl-develbefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl-devel-enginebefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl-fips-provider-upstreambefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl-libsbefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl-perlbefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl3before 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl3-develbefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl3-devel-enginebefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1
Red Hat:hummingbird:1openssl3-libsbefore 0:3.5.9-0.1.hum10:3.5.9-0.1.hum1

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-2026-35189Sep 29, 2026 · Excessive Memory Allocation in Relative CRLDP Processing
    21Monitor
  • ← EarlierCVE-2026-35191Sep 29, 2026 · QUIC Unvalidated Amplification Credit may be Over Accounted
    14Monitor
  • Later →CVE-2026-54872Sep 29, 2026 · Timing Side-Channel in Scalar Multiplication for Non-NIST EC Curves
    14Monitor

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 OpenSSL3.4.8Vendor (CNA)
OpenSSL OpenSSL3.5.9Vendor (CNA)
OpenSSL OpenSSL3.6.5Vendor (CNA)
OpenSSL OpenSSL4.0.3Vendor (CNA)
azl3 openssl 3.3.7-6 on Azure Linux 3.03.3.7-7 · Release NotesMicrosoft (MSRC)
debian:openssl3.5.7-1~deb13u3 · Debian:13Package registry (OSV)
red hat:openssl0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-config-fips0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-devel0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-devel-engine0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-fips-provider-upstream0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-libs0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl-perl0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl30:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl3-devel0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl3-devel-engine0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:openssl3-libs0:3.5.9-0.1.hum1 · Red Hat:hummingbird:1Package 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.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 4, 2026+36 d
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.

No nightly-computed relations.

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.

All national notices →

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-407 · Inefficient Algorithmic Complexity

CVSS 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.

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

Change log

  1. CVSS— → 5.3
  2. Severity— → medium
  3. SSVC exploitation— → none
  4. Exploit maturity— → none
  5. Fix✗ → ✓

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

References

Show all references (4 more)

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

All records