CVE-2023-26103

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 1.2%, top 34% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this weekElevated
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 5.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Versions of the package deno before 1.31.0 are vulnerable to Regular Expression Denial of Service (ReDoS) due to the upgradeWebSocket function, which contains regexes in the form of /s*,s*/, used for splitting the Connection/Upgrade header. A specially crafted Connection/Upgrade header can be used to significantly slow down a web socket server.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
—
EPSS
65.7%
KEV
Not listed

Published

February 25, 2023

Last Modified

March 11, 2025

References (10)

Affected Packages

(1 across 1 ecosystem)
crates.io(1)
PackageVulnerable rangeFixed inDependents
deno—1.31.0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 45× 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.

Showing the most recent 100 of 104 total refreshes for this CVE.

  1. 2026-07-22 23:08 UTCEG score recompute
  2. 2026-07-22 14:06 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2023-26103?
CVE-2023-26103 is a medium vulnerability published on February 25, 2023. Versions of the package deno before 1.31.0 are vulnerable to Regular Expression Denial of Service (ReDoS) due to the upgradeWebSocket function, which contains regexes in the form of /s,s/, used for splitting the Connection/Upgrade header. A specially crafted Connection/Upgrade header can be used to…
When was CVE-2023-26103 disclosed?
CVE-2023-26103 was first published in the National Vulnerability Database on February 25, 2023, with the most recent update on March 11, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-26103 actively exploited?
CVE-2023-26103 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 65.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2023-26103?
CVE-2023-26103 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2023-26103?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-26103, 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.

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