VulnerabilityPublished 9 Nov 2026

CVE-2026-63475: isomorphic-git · Circular symbolic references cause non-terminating resolution (DoS)

Affects isomorphic-gitSource GCVE Database

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Authoritative record:CVE-2026-63475· Medium 4.3

Not known to be exploited · CVSS 4.3 Medium : upgrade to 1.38.6 when convenient.

Data as of 9 Nov 2026, 23:24 UTC

CVSS 3.1 base score

4.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	4.3

EPSS: 0.3% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.38.6

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade isomorphic-git to 1.38.6.

Affected software

Product	Affected	Fixed in
npmisomorphic-git	Affected <1.38.6	Fixed in 1.38.6

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade isomorphic-git to version 1.38.6 or later, where this issue is fixed. The fix includes adding cycle detection and/or a default maximum depth in GitRefManager.resolve() to prevent infinite loops. Avoid cloning from untrusted or compromised Git servers until patched.

Description

isomorphic-git versions prior to 1.38.6 are vulnerable to a denial of service caused by circular symbolic references. A malicious server can advertise symrefs that reference each other in a loop, which are then written to disk by the client. The GitRefManager.resolve() method does not detect cycles or enforce a default depth limit, causing operations that resolve these refs (e.g., log, status, checkout) to hang indefinitely. This results in a persistent denial of service, rendering the repository unusable until fixed.

Impact

This vulnerability causes a persistent denial of service by making any repository cloned from a malicious or compromised server unusable. After a single clone, circular symbolic references are stored on disk, causing any Git operation that resolves these refs to hang indefinitely. There is no impact on confidentiality or integrity, but availability is severely affected.

Summary

The vulnerability in isomorphic-git arises from its GitRefManager.resolve() function, which follows symbolic references without cycle detection or a default maximum depth. A malicious or compromised Git server can supply circular symrefs (e.g., ref A points to ref B and ref B points back to ref A). These circular references are persisted on disk during clone operations. Subsequent Git operations that resolve these refs enter an infinite loop, causing the application to hang indefinitely. This behavior diverges from canonical Git, which caps symref resolution depth and warns on dangling symrefs. The issue is tracked as CVE-2026-63475 and fixed in isomorphic-git version 1.38.6.

CWE-674Uncontrolled Recursion (opens in a new tab)
Class weakness
The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.
Implementation
Ensure that an end condition will be reached under all logic conditions. The end condition may include checking against the depth of recursion and exiting with an error if the recursion goes too deep. The complexity of the end condition contributes to the effectiveness of this action.
Implementation
Increase the stack size.
Attack patterns
Serialized Data with Nested Payloads (opens in a new tab)
Oversized Serialized Data Payloads (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-835Loop with Unreachable Exit Condition (Infinite Loop) (opens in a new tab)
Base weakness
The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Nov 2026, 22:49 UTC

WeaknessesCWE-674, CWE-835

Technical details

References

Community reviews

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