# @asymmetric-effort/specifyjs localhost bypass in SSRF check

Source: https://junglewise.ai/threats/asymmetric-effort-specifyjs-localhost-bypass-in-ssrf-check-63583c44  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-02. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 4 · Published 2026-07-02

@asymmetric-effort/specifyjs is a Node.js library used to prevent server-side request forgery (SSRF) attacks by validating URLs before fetching them. A flaw in its localhost exemption logic failed to recognize IPv6 loopback addresses, the 127.0.0.0/8 range, and 0.0.0.0, allowing attackers to bypass security controls and trigger requests to internal services.

Technologies: [Asymmetric Effort Specifyjs](https://junglewise.ai/threats/technologies/specifyjs), [@asymmetric-effort/specifyjs (npm)](https://junglewise.ai/threats/technologies/asymmetric-effort-specifyjs). Vendors: [Asymmetric Effort](https://junglewise.ai/threats/vendors/asymmetric-effort), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 4, published 2 July 2026.

**Which products and versions are affected?** Asymmetric Effort Specifyjs < 0.2.136; @asymmetric-effort/specifyjs (npm) SEMVER:introduced=0,fixed=0.2.136.

**Is there a fix for This vulnerability?** Yes. @asymmetric-effort/specifyjs (npm): upgrade to 0.2.136 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network.

**Am I affected?** Check whether you run Asymmetric Effort Specifyjs or @asymmetric-effort/specifyjs (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @asymmetric-effort/specifyjs (npm): upgrade to 0.2.136 or later

  ```sh
  npm install @asymmetric-effort/specifyjs@0.2.136
  ```


## Technical details

The vulnerability is a Server-Side Request Forgery (SSRF) bypass caused by incomplete localhost detection in the secureFetch function (core/src/shared/secure-fetch.ts:52-54). The code checked for localhost and 127.0.0.1 only, missing IPv6 localhost ([::1]), the full 127.0.0.0/8 loopback range, and 0.0.0.0. An unauthenticated network attacker can craft requests using these undetected localhost addresses to bypass SSRF protections and access internal services. The fix, released in v0.2.136, expands localhost detection to cover all valid loopback addresses and ranges.

## Affected products

- asymmetric-effort specifyjs < 0.2.136

## Timeline

- 2026-05-29: disclosed
- 2026-05-29: patched: v0.2.136 released

## References

- [https://github.com/asymmetric-effort/specifyjs/security/advisories/GHSA-xw57-23p8-9wc5](https://github.com/asymmetric-effort/specifyjs/security/advisories/GHSA-xw57-23p8-9wc5)
- [https://github.com/asymmetric-effort/specifyjs/commit/25d1fb491d99479efdf501f5f75e0bb80c908f0a](https://github.com/asymmetric-effort/specifyjs/commit/25d1fb491d99479efdf501f5f75e0bb80c908f0a)

## Related threats

- [Asymmetric Effort SpecifyJS CSS sanitization bypass in renderToString](https://junglewise.ai/threats/cve-2026-50290-asymmetric-effort-specifyjs-css-sanitization-bypass-in)
- [SpecifyJS SSRF via URL validation bypass in secure-fetch](https://junglewise.ai/threats/cve-2026-50288-specifyjs-ssrf-via-url-validation-bypass-in-secure-fetch)
- [@asymmetric-effort/specifyjs redirect SSRF in secureFetch](https://junglewise.ai/threats/asymmetric-effort-specifyjs-redirect-ssrf-in-securefetch-09dbb315)
- [@asymmetric-effort/specifyjs unrestricted data URI memory exhaustion](https://junglewise.ai/threats/asymmetric-effort-specifyjs-unrestricted-data-uri-memory-exhaustion-47844f22)
- [@asymmetric-effort/specifyjs information disclosure via console warnings](https://junglewise.ai/threats/asymmetric-effort-specifyjs-information-disclosure-via-console-warnings-1afedf35)