# CVE-2026-89011: isomorphic-git < 1.42.0 Prototype Pollution via getRemoteInfo

Status: published. Published: 2026-09-10. Updated: 2026-11-08.

isomorphic-git before 1.42.0 contains a prototype pollution vulnerability in the getRemoteInfo function that allows a malicious Git server operator to pollute Object.prototype by advertising crafted ref names containing '__proto__' path segments during ref negotiation. Attackers controlling a Git server can advertise a specially crafted ref such as '__proto__/corsProxy' to reroute all subsequent network operations through an attacker-controlled proxy, causing isomorphic-git to invoke the victim's onAuth callback and transmit credentials to the attacker when the victim calls getRemoteInfo with an attacker-supplied URL.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/isomorphic-git/isomorphic-git/pull/2426
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/isomorphic-git/isomorphic-git/commit/b3db111885230bac9a648e0a2312c65ca66f76eb

## Affected products and versions

- isomorphic-git / isomorphic-git (isomorphic-git/isomorphic-git): ≥ 0; < 1.42.0 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 7.1 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.1 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: 0.44% as of 2026-11-08; percentile 38.74%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-1321

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/isomorphic-git/isomorphic-git/security/advisories/GHSA-83vg-jxvh-fx76 (CNA: VulnCheck; vendor-advisory)

- https://github.com/isomorphic-git/isomorphic-git/releases/tag/v1.42.0 (CNA: VulnCheck; release-notes)

- https://github.com/isomorphic-git/isomorphic-git/pull/2426 (CNA: VulnCheck; issue-tracking, patch)

- https://github.com/isomorphic-git/isomorphic-git/commit/b3db111885230bac9a648e0a2312c65ca66f76eb (CNA: VulnCheck; patch)

- https://www.vulncheck.com/advisories/isomorphic-git-prototype-pollution-via-getremoteinfo (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-89011; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-89011; retrieved 2026-11-08; source updated Not reported

Revision: 0a62a9e77b412aa869e67ef6ce02df3940c01d82a752fbab476bcf6cb59a89a3

Canonical: https://y2.dev/cve/CVE-2026-89011

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