isomorphic-git: Circular symbolic references cause non-terminating resolution (DoS)
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- Proof of concept public, per CISA
- Fix
- Fixed in 1.38.6
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 1.38.6.
- Exploitation15/40CISA rates a proof of concept as public
- Exposure7/25Reachable over the network without a login · Data gap: No advisory context yet
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity4.3/10CVSS 4.3
- No patch0/5No signal
What would change the score
- Would score about 66 if added to CISA KEV
- Would score about 61 if CISA's SSVC rates exploitation active
- Would score about 41 if advisories confirm default setups are exposed
CVE-2026-63475 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 4.3 (medium) and affects isomorphic-git; fixed in 1.38.6.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 26/100 · provisional
- Fix
- Fixed in 1.38.6
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: poc
- Automatable: no
- Technical impact: partial
Summary
isomorphic-git, a pure JavaScript Git implementation used in Node.js and browser applications, is affected. A malicious or man-in-the-middle-controlled remote can cause circular symbolic references to be stored in a cloned repository, leading operations such as log, status, checkout, and branch to hang indefinitely and leaving the repository unusable.
Read the original description
isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers. Prior to 1.38.6, isomorphic-git persists server-supplied circular symref= capabilities through updateRemoteRefs, and GitRefManager.resolve() follows the resulting loose symbolic references without a default depth limit or cycle detection. After a clone from a malicious or man-in-the-middle-controlled remote, operations such as log, status, checkout, and branch that resolve refs/remotes/origin/a or refs/remotes/origin/b do not terminate. The circular references remain on disk, leaving the repository unusable for the application and causing a persistent denial of service. This issue is fixed in version 1.38.6.
What to do
Upgrade to a fixed version: 1.38.6.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: poc · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- isomorphic-git isomorphic-git
fixed in 1.38.6
Evidence 4
- Advisory
- Repository
- Repository
- Repository
Corrections
None so far.
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Questions about CVE-2026-63475
Is CVE-2026-63475 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-63475?
isomorphic-git: before 1.38.6.Source: cve.now feed data
How do I fix CVE-2026-63475?
Upgrade to a fixed version: 1.38.6.Source: cve.now feed data