modern-tar 0.3.5 through 0.8.5 contains a memory exhaustion vulnerability that allows attackers to produce negative entry sizes via non-octal bytes parsed by readOctal(). Attackers can supply a crafted, optionally gzip-compressed, archive to unpackTar() that buffers chunks indefinitely, exhausting process memory and suppressing later entries.
CVE-2026-109380
HIGHPre-NVD 7.57.5Trending — 4 sources updated this week
EchelonGraph scoreHIGH confidence
“—” beside the score: it is equal to the CVSS score beside it.
Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-10-12. A secondary CVSS source baseline 7.5; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: GitHub Security Advisory, a secondary CVSS source
7.5EG
EchelonGraph verdictPlan mitigationRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: None knownExposed services: Not assessed
An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHhigh confidence
- EG Risk
- 49EG Risk 49/100
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 (value × EchelonGraph’s weight)Severity75% × 45%The EG Score, 7.5 of 10.Exploitation0% × 40%No KEV listing, EG-KEV tier or EPSS when EchelonGraph scored this CVE.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high until it ships, then apply the release. - EPSS PROB
- 0.4%
- EPSS %ILE
- 37th
- KEV
- Not listed
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high until it ships, then apply the release.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
October 12, 2026
Last Modified
October 13, 2026
Advisory Details (5)
Auto-updated Oct 12, 2026Upstream fix merged — awaiting tagged release. Sources: github_commit, github_pr.
Web page
modern-tar 0.3.5 through 0.8.5 Memory Exhaustion via Malformed Octal Size Field | Advisories | VulnCheck
https://www.vulncheck.com/advisories/modern-tar-0.3.5-through-0.8.5-memory-exhaustion-via-malformed-octal-size-fieldGitHub pull request
fix(tar): reject malformed octal fields
Fix merged in ayuhito/modern-tar PR #195 on 2026-10-08 — awaiting tagged release
https://github.com/ayuhito/modern-tar/pull/195GitHub commit
commit 181c8cb75351 (ayuhito/modern-tar)
Fix landed in ayuhito/modern-tar commit 181c8cb75351 — awaiting tagged release
https://github.com/ayuhito/modern-tar/commit/181c8cb75351867535057817ada4802a90fe416eWeb page
modern-tar/src/tar/encoding.ts at v0.8.5 · ayuhito/modern-tar · GitHub
https://github.com/ayuhito/modern-tar/blob/v0.8.5/src/tar/encoding.tsWeb page
GitHub - ayuhito/modern-tar: 🗄 Zero dependency streaming tar parser and writer for every JavaScript runtime. · GitHub
https://github.com/ayuhito/modern-tarVendor Advisories for CVE-2026-109380(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 8× in last 7d / 8× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
- 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-13 16:28 UTCEG score recompute
- 2026-10-13 16:28 UTCGHSA enrichmentGHSA-m6wr-6wgx-82mm · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-13 15:56 UTCEG score recompute
- 2026-10-13 15:56 UTCGHSA enrichmentGHSA-m6wr-6wgx-82mm · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-12 21:26 UTCEG score recompute
- 2026-10-12 21:02 UTCEG score recomputeFirst assessed: 7.5 HIGH
- 2026-10-12 20:59 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-109380?
CVE-2026-109380 is a high-severity vulnerability; its CVE record was published on October 12, 2026. modern-tar 0.3.5 through 0.8.5 contains a memory exhaustion vulnerability that allows attackers to produce negative entry sizes via non-octal bytes parsed by readOctal(). Attackers can supply a crafted, optionally gzip-compressed, archive to unpackTar() that buffers chunks indefinitely, exhausting…
When was CVE-2026-109380 made public?
CVE-2026-109380 was made public on October 8, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on October 12, 2026. EchelonGraph's copy of the record carries a last-modified date of October 13, 2026; the record at its source may have been updated since.
Is CVE-2026-109380 actively exploited?
CVE-2026-109380 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (37th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-109380?
CVE-2026-109380 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-109380?
An upstream fix for CVE-2026-109380 has been merged but is not yet in a tagged release. Until it ships, restrict network exposure of the affected system or apply the vendor's mitigation, then update to the release that contains the fix. The vendor advisories EchelonGraph has for CVE-2026-109380 are linked in the Vendor Advisories panel on this page.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-109380
Is Your Infrastructure Affected by CVE-2026-109380?
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