CVE-2026-27601
published 2026-03-03CVE-2026-27601: Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very…
PriorityP335medium5.9CVSS 3.1
AVNACHPRNUINSUCNINAH
EPSS
0.61%
45.4th percentile
Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth limit is passed as the second argument to _.flatten. In the case of _.isEqual, the vulnerability can only be exploited if there exists a code path in which two distinct datastructures that were submitted by the same remote client are compared using _.isEqual. For example, if a client submits data that are stored in a database, and the same client can later submit another datastructure that is then compared to the data that were saved in the database previously, OR if a client submits a single request, but its data are parsed twice, creating two non-identical but equivalent datastructures that are then compared. Exceptions originating from the call to _.flatten or _.isEqual, as a result of a stack overflow, are not being caught. This vulnerability is fixed in 1.13.8.
Affected
16 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | underscore | < underscore 1.13.8~dfsg+~1.13.0-1 (forky) | underscore 1.13.8~dfsg+~1.13.0-1 (forky) |
| jashkenas | underscore | < 1.13.8 | 1.13.8 |
| msrc | azl3_boost_1.83.0-2_on_azure_linux_3.0 | — | — |
| msrc | azl3_cyrus-sasl-bootstrap_2.1.28-8_on_azure_linux_3.0 | — | — |
| msrc | azl3_cyrus-sasl_2.1.28-8_on_azure_linux_3.0 | — | — |
| msrc | azl3_krb5_1.21.3-3_on_azure_linux_3.0 | — | — |
| msrc | azl3_numpy_1.26.3-4_on_azure_linux_3.0 | — | — |
| msrc | azl3_rsyslog_8.2308.0-5_on_azure_linux_3.0 | — | — |
| msrc | cbl2_cyrus-sasl-bootstrap_2.1.28-4_on_cbl_mariner_2.0 | — | — |
| msrc | cbl2_cyrus-sasl_2.1.28-4_on_cbl_mariner_2.0 | — | — |
| msrc | cbl2_python-sphinx_4.4.0-3_on_cbl_mariner_2.0 | — | — |
| msrc | cbl2_python-sqlalchemy_1.4.32-2_on_cbl_mariner_2.0 | — | — |
| msrc | cbl2_rsyslog_8.2204.1-4_on_cbl_mariner_2.0 | — | — |
| underscorejs | underscore | < 1.13.8 | 1.13.8 |
| underscorejs | underscore | >= 0 < 1.13.8~dfsg+~1.13.0-1 | 1.13.8~dfsg+~1.13.0-1 |
| underscorejs | underscore | >= 0 < 1.13.8 | 1.13.8 |
CVSS provenance
nvdv3.15.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
nvdv4.08.2HIGHCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
osv8.2HIGH
vendor_debian8.2HIGH
vendor_redhat8.2HIGH
vendor_msrc7.5HIGH
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Microsoft
Underscore.js has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
vendor_msrc·2026-03-10·CVSS 7.5
CVE-2026-27601 [HIGH] CWE-770 Underscore.js has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
Underscore.js has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
Mariner: Mariner
GitHub_M: GitHub_M
Customer Action Required: Yes
Red Hat
Underscore.js: Underscore.js: Denial of Service via recursive data structures in flatten and isEqual functions
vendor_redhat·2026-03-03·CVSS 8.2
CVE-2026-27601 [HIGH] CWE-606 Underscore.js: Underscore.js: Denial of Service via recursive data structures in flatten and isEqual functions
Underscore.js: Underscore.js: Denial of Service via recursive data structures in flatten and isEqual functions
Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth li
Debian
CVE-2026-27601: underscore - Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.f...
vendor_debian·2026·CVSS 8.2
CVE-2026-27601 [HIGH] CVE-2026-27601: underscore - Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.f...
Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth limit is passed as the second argument to _.flatten. In the case of _.isEqual, the vulnerability can only be explo
OSV
CVE-2026-27601: Underscore
osv·2026-03-03·CVSS 8.2
CVE-2026-27601 [HIGH] CVE-2026-27601: Underscore
Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth limit is passed as the second argument to _.flatten. In the case of _.isEqual, the vulnerability can only be explo
GHSA
Underscore has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
ghsa·2026-03-03
CVE-2026-27601 [HIGH] CWE-674 Underscore has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
Underscore has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
### Impact
In simple words, some programs that use `_.flatten` or `_.isEqual` could be made to crash. Someone who wants to do harm may be able to do this on purpose. This can only be done if the program has special properties. It only works in Underscore versions up to 1.13.7. A more detailed explanation follows.
In affected versions of Underscore, the `_.flatten` and `_.isEqual` functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow.
A proof of concept (PoC) for this type of attack with `_.isEqual`:
```js
const _ = require('underscore');
// build JSON string fo
OSV
Underscore has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
osv·2026-03-03
CVE-2026-27601 [HIGH] Underscore has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
Underscore has unlimited recursion in _.flatten and _.isEqual, potential for DoS attack
### Impact
In simple words, some programs that use `_.flatten` or `_.isEqual` could be made to crash. Someone who wants to do harm may be able to do this on purpose. This can only be done if the program has special properties. It only works in Underscore versions up to 1.13.7. A more detailed explanation follows.
In affected versions of Underscore, the `_.flatten` and `_.isEqual` functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow.
A proof of concept (PoC) for this type of attack with `_.isEqual`:
```js
const _ = require('underscore');
// build JSON string fo
No detection rules found.
No public exploits indexed.
Bleepingcomputer
Microsoft March 2026 Patch Tuesday fixes 2 zero-days, 79 flaws
blogs_bleepingcomputer·2026-03-10·CVSS 8.8
[HIGH] Microsoft March 2026 Patch Tuesday fixes 2 zero-days, 79 flaws
## Microsoft March 2026 Patch Tuesday fixes 2 zero-days, 79 flaws
## Lawrence Abrams
The number of bugs in each vulnerability category is listed below:
46 Elevation of Privilege Vulnerabilities
2 Security Feature Bypass Vulnerabilities
18 Remote Code Execution Vulnerabilities
10 Information Disclosure Vulnerabilities
4 Denial of Service Vulnerabilities
4 Spoofing Vulnerabilities
When BleepingComputer reports on Patch Tuesday security updates, we only count those released by Microsoft today. Therefore, the number of flaws does not include 9 Microsoft Edge flaws, Mariner, Payment Orchestrator Service, Azure, and Microsoft Devices Pricing Program flaws fixed earlier this month.
To learn more about the non-security updates released today, you can review our dedicated articles on the
Wiz
CVE-2026-27601 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 8.2
CVE-2026-27601 [HIGH] CVE-2026-27601 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-27601 :
JavaScript vulnerability analysis and mitigation
Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no finite depth limit is passed as the second argument to _
Bugzilla
CVE-2026-27601 Underscore.js: Underscore.js: Denial of Service via recursive data structures in flatten and isEqual functions
bugzilla·2026-03-03·CVSS 5.9
CVE-2026-27601 [MEDIUM] CVE-2026-27601 Underscore.js: Underscore.js: Denial of Service via recursive data structures in flatten and isEqual functions
CVE-2026-27601 Underscore.js: Underscore.js: Denial of Service via recursive data structures in flatten and isEqual functions
Underscore.js is a utility-belt library for JavaScript. Prior to 1.13.8, the _.flatten and _.isEqual functions use recursion without a depth limit. Under very specific conditions, detailed below, an attacker could exploit this in a Denial of Service (DoS) attack by triggering a stack overflow. Untrusted input must be used to create a recursive datastructure, for example using JSON.parse, with no enforced depth limit. The datastructure thus created must be passed to _.flatten or _.isEqual. In the case of _.flatten, the vulnerability can only be exploited if it is possible for a remote client to prepare a datastructure that consists of arrays at all levels AND if no
2026-03-03
Published