CVE-2026-18798

HIGHPre-NVD 7.57.5
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-08-25. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 6 sources updated this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: None knownExposed: 0

A fix is available — apply it.

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.

CVSS v3
7.5
EG Score
7.5(high)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
72%
KEV
Not listed

Published

August 25, 2026

Last Modified

August 25, 2026

Advisory Details (4)

Auto-updated Aug 25, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
github_commit

commit 967582d5037f (openssl/openssl)

Fix landed in openssl/openssl commit 967582d5037f — awaiting tagged release

https://github.com/openssl/openssl/commit/967582d5037f01a26b6d19beae19af62a1b15c3c
github_commit

commit 70cebd74d359 (openssl/openssl)

Fix landed in openssl/openssl commit 70cebd74d359 — awaiting tagged release

https://github.com/openssl/openssl/commit/70cebd74d3592f5272945501b58a60374c4e13af
github_commit

commit a14a1deac403 (openssl/openssl)

Fix landed in openssl/openssl commit a14a1deac403 — awaiting tagged release

https://github.com/openssl/openssl/commit/a14a1deac403522fbeafabcb198503cf6caa7dc4

Vendor Advisories for CVE-2026-18798(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuopenssl-provider-legacy (3.5.5-1ubuntu3.4) @ resolute2026-08-26ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 12× in last 7d / 12× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-26 16:34 UTCEG score recompute
  2. 2026-08-26 16:34 UTCVendor advisory
  3. 2026-08-26 16:34 UTCGHSA enrichment
  4. 2026-08-26 14:46 UTCEPSS rescore
  5. 2026-08-26 03:56 UTCEG score recompute
  6. 2026-08-26 03:56 UTCVendor advisory
  7. 2026-08-26 03:56 UTCGHSA enrichment
  8. 2026-08-25 14:35 UTCEG score recompute 7.50
  9. 2026-08-25 14:34 UTCMITRE cvelistV5CVSS v3 → 7.5 · severity → HIGH
  10. 2026-08-25 13:21 UTCNVD update
  11. 2026-08-25 13:16 UTCEG score recompute
  12. 2026-08-25 13:15 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-18798?
CVE-2026-18798 is a high vulnerability published on August 25, 2026. 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…
When was CVE-2026-18798 disclosed?
CVE-2026-18798 was first published in the National Vulnerability Database on August 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18798 actively exploited?
CVE-2026-18798 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 28.0% of all scored CVEs.
What is the CVSS score of CVE-2026-18798?
CVE-2026-18798 has a CVSS v3.1 base score of 7.5 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-18798?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-18798, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-18798

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